Another engine miss issue (Page 2/4)
Another One MAY 01, 11:49 AM
Thermostat is 180 degree

I did cap the EGR vacuum with no change. I have ordered another EGR tube and gaskets incase there is something there I can't see. Also ordered the SS vacuum lines to help eliminate that as a problem. Some of the vacuum fittings are in pretty poor shape so I'll replace those with generics from O'Reilly, unless someone has a better idea.

I cleaned and added a ground connection from engine to frame but I did not dielectric grease them. Hope to get to that today. While I'm at it I will confirm "Tan" wire bolted to block is clean and dielectric greased.

I tried the MAP test using the vacuum from air powered brake bleeder but it is to much vacuum so I need to repeat the test with a hand vacuum pump.

I said MAF sensor when I meant ACT sensor (on the side of the air filter can). I checked all temp sensors this morning with the scanner and they are within 1 C of each other.

Thanks again for the ideas.
Another One MAY 01, 09:26 PM
theogre
Thanks for your input. There is a "Tan" wire bolted to the head under the exhaust cross over. It is crimped in a ring terminal (looks factory) with a black wire in the same harness. I removed the terminal from the head, inspected it for damage (none) pulled on it to make sure the crimp was good, sanded it shiny and around the hole in the head. Dielectric in the hole, on the bolt and all over the terminal ring. Did the same thing for the battery ground to the head, battery ground to the frame, head to the frame, frame to trunk lid, black wire from the same wire bundle as the tan wire to transmission. I couldn't find any others.

Idle fluctuation improved from around 300 RPM to 150 RPM (900 - 1050 now) and at higher RPMs the miss is not as bad. O2 runs between 437 mv and 452 mv depending on throttle work.

1 good backfire coming down from 2000 RPM opened the original muffler so that's now on the list.

Still need to do the MAP vacuum test and swap to the copper core plugs.

Again thanks to everyone for the input. For the first time in months it feels like I'm making progress.
olejoedad MAY 01, 09:43 PM
O2 reading should jump rapidly between negative and positive mV readings.
Skybax MAY 01, 10:00 PM

quote
Originally posted by Another One:

I agree on the O2 sensor but I only found about it last night as it is not setting a code.





quote
Originally posted by Another One:

O2 sensor has been replaced and there is no change in condition.




O2 won't throw a code unless its beyond dead, maintenance item that should be replaced due to age, the cross counts on a good 02 should fluctuate like crazy.

And nowadays the AC Delco and Bosch O2s are both garbage, the Denzo is the only one you want (not universal, make sure it has OEM connector).

https://www.autozone.com/en...-234-1001/707266_0_0


quote
Originally posted by Another One:

1 good backfire coming down from 2000 RPM opened the original muffler so that's now on the list.




Ouch! Maybe you can find a good used original stainless muffler to swap it out (cheaper than aftermarket route).

Your condition sounds like a classic ignition coil even though you replaced it with several used and a new one, what brand did you buy?

For a stock replacement ignition coil the Standard Blue Streak made in Poland is better build quality than most these days (they are black now and no longer blue).

https://www.oreillyauto.com...c-fiero?q=coil&pos=2

Double check your firing order (and I mean not just the plug wires)...

[This message has been edited by Skybax (edited 05-01-2022).]

Another One MAY 02, 02:45 PM
New coil is a blue streak. Not sure where RockAuto got it from.
Firing order has been verified. Pulling any one wire makes a noticeable difference.
Not sure on the O2 sensor. Original was stuck at 450 mv. New O2 sensor changes but not like suggested above.
I'm hoping the new vacuum lines and EGR tube fix the remaining miss issue.
Forrest MAY 03, 02:59 PM

quote
Originally posted by Another One:

Thermostat is 180 degree

I did cap the EGR vacuum with no change. I have ordered another EGR tube and gaskets incase there is something there I can't see. Also ordered the SS vacuum lines to help eliminate that as a problem. Some of the vacuum fittings are in pretty poor shape so I'll replace those with generics from O'Reilly, unless someone has a better idea.

I cleaned and added a ground connection from engine to frame but I did not dielectric grease them. Hope to get to that today. While I'm at it I will confirm "Tan" wire bolted to block is clean and dielectric greased.

I tried the MAP test using the vacuum from air powered brake bleeder but it is to much vacuum so I need to repeat the test with a hand vacuum pump.

I said MAF sensor when I meant ACT sensor (on the side of the air filter can). I checked all temp sensors this morning with the scanner and they are within 1 C of each other.

Thanks again for the ideas.



EGR: I blocked mine off at the tube going into the upper intake manifold with a cutout from a coke can. That fixed my high idle issue till the new tube came in, but I dunno that it will cause a misfire.
No fuel pressure at key on: There are two relays in the engine bay on the driver side. One is the AC relay and the other is the fuel pump relay. Your fuel pump relay is out. To test you can swap them.

(I am chasing a miss myself at the moment)

On my sons 88 it was missing bad! This was fixed by pulling the fuel rail and using a shrinkwrap contraption/w carb cleaner and a 9V battery to clean the injectors. Both ways....
Replaced those and the car ran a lot better afterward...still missed on one cylinder. Screwdriver on the injector and my ear to it confirmed the injector was fried. (Dunno how this was missed while cleaning...I blame the kid.)

Have you checked that all the injectors are ticking? 1 3 and 5 are easy to get to....3 and 5 for sure. Tickles my brain a bit that they are not firing and they all ride the same fuse.
Have you pulled the fuel rail and cleaned it/the injectors? Injectors might be toast or clogged. How old is your fuel pressure regulator? Might wanna swap that out while you're in there.

[This message has been edited by Forrest (edited 05-03-2022).]

Another One MAY 04, 12:49 AM
Forrest,
I appreciate the input. All injectors were cleaned at about 75 psi with solvent. I have a friend that has a device that holds solvent and feeds it to the injector at 75 psi and fires the injector every few seconds (out of the engine). All spray patterns were great. Nice even ring of mist when they fired. In the engine, all 6 injectors are ticking away. I believe even when there is no spark to burn the fuel.

EGR tube and gaskets have been ordered as well as the SS vacuum lines from Rodney. The EGR is new and has no vacuum on it but that doesn't fix a tube leak..

Cleaning and greasing all grounds (Thanks Ogre) made a big improvement but didn't correct it all. I'm hoping the new vacuum lines, fittings, and EGR tube remedy the issue.

I'm used to load on the engine making the problem worse but in this case it gets better. I got a second gear squeal during hard acceleration the other day (I was smiling for a moment). In my opinion, the ECU is getting bad data from somewhere. Just don't know how to determine where. Possible vacuum leak but hosing down the engine with carb cleaner didn't change anything.

I still need to do the MAP test with a hand vacuum pump. Where did I put that damn thing. It's a small garage after all. Where did all this *stuff* come from?
theogre MAY 04, 09:04 AM
Fix ground other places like G201 G202 in the cabin too.
See my Cave, Wire Service

F-pump and more goes thru them. Need long screw/nut driver w/ magnet tip to get at 1 behind radio.

Test volts at battery and alt out. You still have Hunting Idle and Flaky Power is a good way to have this problem.
Battery & Alt out should be ~ 14.7v w/ engine running. And should have same or Very close to same.
ECM should see about same when scanned. If not still have power ground or both w/ problems. (Scan read is often bit different vs a meter on wires.)
Still reports volts wrong could be ECM dying slowly. Just 1 Crack solder joints or part in it can do odd things or completely kill ECM.

Note: Fixing/cleaning grounds etc can cause ECM to reset idle and not run right until drive above 35mph.
(Some reset idle even run while parked but can't be sure engine sees right conditions but drive > 35mph will make sure.)

[This message has been edited by theogre (edited 05-04-2022).]

Another One MAY 15, 12:18 PM
New EGR tube and SS vacuum lines installed with no change. Except the coolant leak I created on one of the throttle body rubber coolant hoses.

Voltage at alternator and battery is 14.5V. Scanner says the ECU is reporting 14.2V so I'll go after the cabin grounds next.

Passenger headlight only went about 1/2 way up and lots of chugging when it moved. Acted like stripped gear teeth so that's been added to the list as well.
Another One MAY 16, 09:48 PM
Headlight grounds (1 on each side), ECM ground, and that mother behind the stereo all cleaned and dielectric grease applied in liberal amounts. No change.

I did read a tip for setting the timing while I was searching for answers. Put your timing light on the coil to cap wire, then set your timing to 10* BTDC. It makes averaging the 1 and 4 cylinder a lot faster and easier.

I have a Fluke 100 mHZ oscilloscope to check for missing pulses from the ECM but I'm not sure where to check. If anyone has any input I would be extremely grateful. I don't think I can check the pick up coil while it's running but should be able to check ICM to ECM and ECM to coil

Oh yeah, the no fuel at key on was the relay. Several people mentioned that. Thanks to all of them.

[This message has been edited by Another One (edited 05-16-2022).]