Bump ^ Still wondering about the EGR.

My opened from idle to acceleration. I tested it by placing my finger on the diaphragm from under need the dome and revved the engine. I don't know what I took it up to but I felt movement right away.

quote Originally posted by Shonyman32: When should the EGR be open? When accelerating at all from a stop (mildly, TPS at 15, 25%) the EGR reads anywhere from 30 to 50%. At hard throttle it reads zero. Is this normal for the EGR to open when accelerating from a stop?

The EGR valve vacuum is controlled by an ECM operated solenoid. The ECM will turn the EGR "on" and "off" (Duty Cycle) by grounding the EGR solenoid. The duty cycle is calculated by the ECM based on information from the coolant sensor, MAP sensor and engine rpm. The ECM is programmed to only allow EGR at part throttle cruise, not at idle and not at full throttle. The vacuum that affects the EGR valve source is ported (meaning that there's only vacuum when the throttle is open) means that there won't be EGR at idle. The amount of vacuum applied to the EGR valve is varied by controlling the amount of time that the solenoid is open compared to being closed.

quote [B]The car starts to run normal at a temp. around 105 F. I think my thermostat is bad because I never reach even 200 F while driving in the city. A 15 min drive 10 min city and 5 min interstate (last part of drive interstate) and then about a half mile off the interstate My temp. never got above 175 F.

My 87 GT, stock 2.8L, runs right at 195 - 200 when driving. When idling at lights, it does get hotter, but the radiator fan kicks and it comes right back down to 200.
You need to check / replace your thermostat. Are you ever in Closed Loop? I drove and did a log last night. I went from Akron to Northfield, about 40 minutes one way mixed driving. The whole log shows my temp at roughly 200 degrees the whole time.
The thermostat limits the lower temperature and the cooling fan limits the upper temperature in a normally functioning system. The ECM is programmed to run most efficient at that temperature range. When you're driving down the road around or over 20 mph, the airflow through the radiator keeps coolant temp at the thermostat rating which is 195°F stock. When idling and with the AC off, the temperature will climb to the stock fan switch temperature of around 235°F, then the fan kicks on. The gauge will climb a tiny bit more then start dropping until about 225°F then the fan turns off. It will stay in that range until you start moving fast enough again.

I think you need to look at your cooling system. You had mentioned early on in this thread you weren't using coolant, did you change to proper coolant mix? You need to check your thermostat; make sure it is 195 degree type. You have mentioned several times an exhaust leak... find it and fix it. The leak can confuse your ECM.

The exhaust leak could be involved with the problem, but I'm not sure it would have much effect when cold. Also check your fuel pressure with key on engine off, and see how it acts when idling, and when opening the throttle. Don't rely on any assumptions that it should be good, see what it's really doing. It should be at both proper pressure, and maintaining a constant differential vs the manifold pressure (you should see it change in response to this).

It looked like you might have found something going on with the MAP sensor, since it was running better when you unplugged it. If you have a vacuum leak it will throw off the MAP reading, especially if it's a leak in the line that leads to the sensor. I might have missed if you already ruled that out.
If you can't find a vacuum leak, and unplugging the MAP makes it run better, you might try replacing the MAP. Keep the original one though, unless you find out for sure that it's actually bad. I agree with earlier comment that they don't seem to fail very often, and given a choice I'd rather have the GM original part.

You mentioned a MAP of 1.1v at idle. Did your scan show the pressure in kPa? I think mine runs in the mid-high 30s at a 1000rpm idle with the datalogging cable connected.
According to the formula suggested here:
https://www.fiero.nl/forum/F...HTML/121946.html#p10
Your 1.1v reading would translate to about 27.25kPa, which I think is low. But that wasn't a perfect formula either, it was an approximation based on a graph. So maybe your kPa reading is actually higher than that.
If the MAP sensor is seeing (because of vacuum leak) or reporting (bad sensor or wiring fault) lower than actual pressure, it would encourage the ECM to deliver less fuel. I say "encourage" because then the O2 feedback would try to compensate for it.

One other thing to check - backprobe the MAP and TPS connectors to make sure you have 5.0v going into them. I don't know which pin but one of them is connected to a regulated 5.0v output. If it's not 5.0V then that could throw off the voltage it sends back to the ECM.


How aggressive is the cam? Between the increased displacement and the cam, it would throw off the factory ECM tune. I don't know if it should be driving the BLMs all the way to 150 though - I'm thinking there might be other problems (like a low MAP reading) that are pushing it that high.
Be careful - 150 is the maximum it can go to. This means the ECM isn't able to add as much fuel as it would like, so it might be lean even under heavy throttle. If it's truly lean then that can be dangerous for the engine under a load.
I'm not sure if you really need 17lb injectors, but they might be preferable for your engine build. Once the whole package is together it would be worth working on a custom ECM tune for your car, but first you need to make sure the mechanical issues are sorted out. Tuning an ECM while there are mechanical/sensor problems can be a waste of time.
ECM tuning is a big subject. If you're interested you might want to read up on that, there's lots of discussions and tutorials over at thirdgen.org and on gearhead-efi. It takes a while to understand it, at least it did for me. But after a while it all starts to make sense. The first and simplest thing you'd probably want to change is your injector base constant. It describes the relationship between the size of your injectors and the engine. The first mod attempt would be to increase that value by a factor of (3.1/2.8).
A more complicated issue you'd want to eventually get into is your VE (volumetric efficiency) table. This describes how efficiently the ECM expects your engine to burn fuel at different combinations of RPM and MAP. It's probably out of calibration for your cam. I've never tried to tune that but I've read it takes a lot of datalogging and experimenting to get it right.
But despite all this, the O2 sensor does provide feedback that can make the engine run "sorta okay". Not ideal though.
Your car runs better when warm - does this happen suddenly at the same moment as it goes into closed loop? If so, the O2 feedback is probably what's helping it to compensate for whatever is wrong.

A neutral BLM/INT is 128. They will stay there until the ECM has entered closed loop.
I would suggest at least replacing the O2 sensor with a new Denso. RockAuto sells them for something like $12+ship. They gradually become less accurate with age, so they should be replaced once in a while. Just a slight improvement in fuel economy will pay for the sensor quickly, it's not like a modern car where the O2 sensors cost a fortune. However, I don't expect that the O2 is causing the problems you're experiencing. It's just something I'd replace if it's very old, and if it helps the problem that's a bonus.

Re: ignition timing - the ECM is reporting the total commanded advance. The 10 degrees you set at the distributor is just the base timing. The ECM will command more advance beyond that depending what it's programmed to do under different conditions. The timing advance you saw sounds normal. Be aware the ECM blindly trusts that the distributor is physically at 10 degrees (or whatever has been specified in the tune). If it's commanding 18 degrees, what it's really commanding is "base timing + 8 degrees." If base timing isn't at 10, then the whole spark advance behavior will be equally offset under all conditions.

quote Originally posted by Shonyman32: I have an exhaust leak. Could the leak be sucking in air and making the 02 sensor look lean? Raising the BLM's? Although my spark plugs look dry.

Or letting out exhaust making the 02 sensor read less exhuast fumes.

I have a few things to post real quick.
Thanks for all the information!

My map and TPS have 5v running to them. My dad checked them because he has all the equipment and he also understands electricity more than me and I didn't want to make a mistake.
I trust his word because he also showed me what to do and how he got 5v. He tested the TPS on his "potentiometer" and the needle moved good throughout the entire swing.

Thank you for the EGR information.

I will test my thermostat and visually compare it to a new one at an autoparts store and if any differences or if it test bad I'll buy a new one. Changed the coolant today.

Fixed the exhaust leak slightly. Probably need a new gasket now though because after crawling under the engine one exhaust bolt was gone. Replaced it and although it is quieter it is not perfect.

My fuel pressure was within spec before I removed the Vac. line to the regulator. Now after I removed the Vac. line to the regulator I am at a solid 43. It definitely runs better when cold with the line unplugged.

About the MAP sensor - The MAP sensor only ran better in neutral with very little load on the engine when put into gear and accelerated I had absolutely zero power and it would hardly move out of a parking spot with it dieing.

I will post the kPa of the MAP sensor at idle as soon as I get it.

About it running lean my spark plugs look dry but they aren't super dry like I have seen on some engines before.

I will post back with information after putting coolant in, checking my thermostat, new 02 sensor, and a reset of the computer with some driving around.

What is the Rich / Lean Counter on WinALDL?

Also the car doesn't start acting right until closed loop and the 02 sensor is warm.

bump

I have lost track of all that you have posted and I am new to this diagnostic of engines but it sound familiar to the engine I have had trouble with. It a Pacifica V6 the valves were shot, time belt broke. Car ran a little better when cold but would not staying running when warm. Plugs were dark and somewhat wet. Changed all the valve started up and samething #^#*}*{£{. I had gotten a white dot of on two side of the crank and timed it out 180 degrees. I was so pissed as anyone can imagine. I don't know just guessing with the long duration ( valves open I would assume). The valves open to long and compression is lost? Again just guessing but trying to learn. Or maybe closed to long?

Bump

Any new thoughts on 17 lb injectors?

bump

Confused, this is a stock 2.8, and you want to put in different lb injectors?

This is not a stock 2.8.
It is a 3.1 block and crank bored .040 over. With a cam possibly. Bought three cams off of someone. 1 used 2 new. I don't know if the new cams were stock or not. Out of the two cams I put the one in with more duration instead of lift because our engines don't flow air well and for reliability.

Maybe the duration is too long?
I'm not real knowledgable about it, but just a speculation.

Could you elaborate a little?

I was told to do this earlier in this thread but I either didn't or didn't do it the right way.
I just put two pieces of cardboard (thin and corrugated) about 1mm thick each in between the throttle body and the TPS. So the computer reads that the throttle is open more than it is and sprays more gas. The car is now idling with out any touch of the throttle. Although it takes longer to crank now about an extra half to full second. I will check my TPS voltage and see how far off of .5 it is now.

You should really invest in a USB-ALDL cable it will help you out a lot with diagnosing problems with sensors. Mine has been invaluable so far.

I am at 1.35 volts on Win ALDL now or 20% open.

cool, did not know that. Mine is at 1.55 volts when at idle.

Shouldn't the TPS showing closed at idle and the IAC controlling the air. I believe mine is at .78 TPS 25 IAC the plate actually looks closed.

The TPS as far as I know should be around .5 volts at idle with you foot off the pedal.

.5-.8 is normal. I've had differet reading on different cars.... shony did you finally resolve your startup issue?

When I originally put the cardboard under the TPS it started up great an idled then after a long drive and a cool down I think the ECM zeroed out the TPS.

I've not returned to the forum for a while, sorry I didn't see your earlier question.
The "rich/lean" counter counts how many times the O2 sensor has cycled between reading rich and reading lean. It counts from 0 to 255, then loops around to 0 again. Looking at that graph tells you how smoothly and quickly the sensor is behaving. Ideally that graph should be smooth, not jagged.
Although the ECM is targeting the stoich point, what really happens is that the mixture keeps alternating between very slightly rich and very slightly lean. Because the O2 sensor is a "narrowband" sensor, it has a dramatic swing in the voltage when the mixture just drifts slightly away from stoich.

I don't know what might be going on with the cold idle. It might truly need more fuel, or maybe more fuel is just masking the real issue.
When it's in open loop, without any O2 feedback, it's fueling the engine blindly. It follows the programming in the ECM without knowing how rich or lean it actually is.
So putting 17lb injectors in would trick it into providing more fuel with the same programming (increasing the fuel by a factor of 17/15). This effect would only last while cold. Once it warms up a bit, the O2 sensor becomes active and starts helping the ECM adjust the mixture.
Once warmed up, your engine apparently still wants more fuel (as indicated by the BLMs being stuck at 150). I don't know if this is because of the displacement and the cam, or if it's because of any possible vacuum leak or other issue. If it truly needs that much more fuel then the 17lb injectors would be a good step towards resolving it.

If you're convinced that everything is mechanically solid, good timing, no vacuum leaks, etc, then I'd probably put the 17lb injectors in. Due to the modifications, you may need to customize a chip to get it running at it's best. If you do swap injectors, make note of the part number on the injectors you put in. It's hard/impossible to read once installed, and you might wish you had that information if you start working on a chip.
There is some risk you can get a warm hunting idle when you swap injectors. I had this happen on my car with the injectors from a 93-95 FBody 3.4L. It was able to be fixed by borrowing some settings from the FBody's ECM programming.

[This message has been edited by armos (edited 08-16-2013).]

My friend is going to lend me one of his spare wideband 02 sensors (possibly if he can find it) so I can see my real AFR.

Everything is mechanically solid 100% except VAC. Leaks. I don't think I have any. I have gone over the engine with pure oxygen and a propane torch (not lit) and no increase in engine rpm's.

Who burns chips?

Fixed exhaust leak. No change.

As I understand it, too much cam duration = wont idle, likes to rev.

http://www.jdmcars.com/tech/lift_duration.pdf

[This message has been edited by 2.5 (edited 08-19-2013).]

Thank you very much for that read. I didn't ever think high duration would cause rough idle so I never looked it up.

So I can't say I nailed it but it sounded awfully close to my bad valves low idle problems and high rev running. What other than changing cams could fix the issue. If higher idle is needed how is that accomplished?

I higher idle would be achieved by opening the throttle set screw.

I remember reading some rule of thumb that cam duration influences the RPM range where it likes to run, and lift influences how peaky/broad the range will be. Long duration I think is also what causes the loping idle on some more aggressive cams.

quote Originally posted by LornesGT: So I can't say I nailed it but it sounded awfully close to my bad valves low idle problems and high rev running. What other than changing cams could fix the issue. If higher idle is needed how is that accomplished?

Idle speed is set in the chip. A rough change to the injector base constant could also be done. In fact, that might mitigate the need for bigger injectors, assuming the existing ones can keep up at WOT, high RPM.
With erratic BLMs like Shoneyman mentioned, it really also needs tuning of the Volumetric Efficiency table. I've never done that but I understand it's a long trial and error process, so it's best done in person. Probably some other settings would also need to be fiddled with. With a good tune, theoretically you'd want to see the BLMs stay close to 128 all the time.

quote Shonyman32 I higher idle would be achieved by opening the throttle set screw.

That will work if you have no other option, but it has you fighting the computer, which isn't really the best way to go about things. The ECM will want the idle at 900rpm, or whatever the chip is calling for, and the IAC valve will be completely closed trying to get the idle down. When it finds it can't control the idle, it will set a trouble code.

[This message has been edited by armos (edited 08-19-2013).]

What do you have to buy to start tuning?

Also I found some old number on my cam in my car right now. I do not know if it was an intake or an exhaust lobe but the lift was about .281-.283.
What is the stock cam? All I could find was this thread https://www.fiero.nl/forum/A...090907-2-088944.html
The thread says

quote I don't have the full specs, however, the lift on the intake side is 0.231 and on the exhaust it's 0.263.

and

quote Stock 2.8L Cam Lobe Lift: Intake = .2626" Overall lift with 1.5 ratio rocker arms = .3939" Exhaust = .2732" Overall with 1.5 ratio rocker arms = .4098" Install valve spring height = 1.575" BTDC = -14.0 ABDC = 30.0 BBDC = 27.5 ATDC = -4.5 It is a flat-tappet, You cannot use roller lifters.

I dont know which one is correct.