http://www.youtube.com/watc...Q57E&feature=related

It starts and idles just fine now. The problem is it won't take ANY throttle now. Everything seems to be working like its suppose to. It was working fine the day before. Even worked great up to when I took this video. About 5 min later we couldn't give it any gas. None. Something had to have gone out. I haven't been able to run any tests yet but was hoping some of you guys could toss out some ideas. Anyone have any?

Fuel pressure?

Also check the MAP sensor and connections.
It may run with it unplugged, but as soon as you give it gas it'll stumble.
Also check your connections at the PCM.

Have you tried letting it idle until it's warmed up and see if the problem is still there? (Thinking "closed loop" might help.)

Do you have a scan tool? Makes troubleshooting infinitely easier.

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Raydar
88 4.9 Formula IMSA Fasback..........................88 3.4 coupe -soon to be something other than red

Read Nealz Nuze! Praise the Lowered!

quote Originally posted by Raydar: Fuel pressure? Also check the MAP sensor and connections. It may run with it unplugged, but as soon as you give it gas it'll stumble. Also check your connections at the PCM. Have you tried letting it idle until it's warmed up and see if the problem is still there? (Thinking "closed loop" might help.) Do you have a scan tool? Makes troubleshooting infinitely easier.

Fuel pressure is good unless the pump died while the car was running. Problem is you can't even ease into the throttle a little. ANY throttle at all and it chokes and tries to die. Almost like the ECM is telling it to.

Connections to the MAP were good. Its a possibility that it went out on me though. I'm going to pick up another from the junk yard to check it out.

Its funny you should ask if we had warmed it up. Thats what we were doing. Just getting it up to temp for its first test drive. It was not the first time it had been warm either so the issue should have showed itself earlier.

No scan tool unfortunately. I do have a check engine light also so I'm probably going to have to borrow or buy one. The car is 125 miles away now so all I can do is get some ideas of things to look for when I get back down there. Its just odd.

EDIT: I just spoke to my Dad and he tried to fire it back up yesterday. It wouldn't start at all. It looks like this problem is worse then I thought. I'll see if he can get a fuel gauge on it for me tomorrow. I'll let you know what I find out. If you can think of anything else to check please don't hesitate to let me know. Thanks guys.

[This message has been edited by Fieroseverywhere (edited 04-24-2008).]

One more suggestion...
Make sure that the piece of hose that connects the pump to the steel tube hasn't split. (Yours might have a "pulsator". That could have failed too, I suppose.) I've heard of those hoses splitting in less than a year, on a new pump installation. Acted just like a bad pump.

OTOH, If you're still running an original pump, I'd just go ahead and replace it.

quote Originally posted by Raydar: One more suggestion... Make sure that the piece of hose that connects the pump to the steel tube hasn't split. (Yours might have a "pulsator". That could have failed too, I suppose.) I've heard of those hoses splitting in less than a year, on a new pump installation. Acted just like a bad pump. OTOH, If you're still running an original pump, I'd just go ahead and replace it.

Its got a pulsator on it. I'm not sure the pump is original or not. Someone had replaced the sending unit with an 88 one and left the extra tube coming off un-attached. When the tank was full the extra gas from expansion went onto the ground. I completed the change to the 88 tank + everything else that goes with it. We just had it out of the car 2 days before that video was taken. I'll probably use whatever the new pump comes with. I was planing on replacing the pump anyway but I figured I could at least test drive the car first. Found a decent price on the AC delco 88-92 corvette pump so I'll be going with that. Thanks again Raydar.

[This message has been edited by Fieroseverywhere (edited 04-24-2008).]

Did you EVER bleed the fuel lines? While you have the gauge stick the drain tube in the fuel fill and hold the button down with Power to pin G on the ALDL. You'll be amazed at how much air will be in there. We had the same problem on a swap. Dang fuel pressure would drop really quick. Well the valve isn't made to hold air just fuel.

quote Originally posted by DIY_Stu: Did you EVER bleed the fuel lines? While you have the gauge stick the drain tube in the fuel fill and hold the button down with Power to pin G on the ALDL. You'll be amazed at how much air will be in there. We had the same problem on a swap. Dang fuel pressure would drop really quick. Well the valve isn't made to hold air just fuel.

The car ran many times over two days before we even had the problem. I did re-make a new set of fuel lines that day so its possible. It did run for about 30 minutes with the new lines before the problem surfaced. The pressure dad read today just wasn't anywhere near where it should be. That pump never sounded like it was going to last anyways. I think it just died. The car will run now but nothing above idle. I'm suprised it runs at all. 5PSI should not be enough to keep it running but it does. I'll double check everything when I get back down to the car. Thanks for the idea.

[This message has been edited by Fieroseverywhere (edited 04-25-2008).]

quote Originally posted by Fieroseverywhere: Fuel pressure gauge confirmed the problem. Pump has gone out on me. If we turn on the key a couple of times we can get the pressure up and the car starts just fine. Once started the pressure drops pretty fast and levels out at about 5PSI. I'm ordering a new pump this week so it should have it fixed pretty soon. I'll keep you posted. Thanks for the suggestions Raydar.

i would replace the pump with a monte carlo 3.1L SFI fuel pump, they flow a little better than the fiero pumps at the correct fuel pressure...

if you use the corvette pump, your fuel pressure will be like 55 psi, way too high, and you will get bad gas economy... you could always get lucky, some of the 4.9L pressure regulators can handle it and keep the pressure below 45 psi, but i doubt it..

[This message has been edited by stickpony (edited 04-25-2008).]

quote Originally posted by stickpony: i would replace the pump with a monte carlo 3.1L SFI fuel pump, they flow a little better than the fiero pumps at the correct fuel pressure... if you use the corvette pump, your fuel pressure will be like 55 psi, way too high, and you will get bad gas economy... you could always get lucky, some of the 4.9L pressure regulators can handle it and keep the pressure below 45 psi, but i doubt it..

Cool. Thanks for the tip. I'll do a bit more research before deciding on the pump. Thanks Aaron.

Here's a few good threads on adding the heated O2, just in case you hadn't seen them. Looks like Aaron uses heated O2 sensors as well.

https://www.fiero.nl/forum/Forum2/HTML/087672.html

https://www.fiero.nl/forum/Forum2/HTML/090504.html

Hope that solves the problem.

Darren

One other thought, fuel pressure regulator.
Normally they go out all at once but it could just bypass pressure occasionally then sometimes hold.

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Mick
1986 GT

My 4.9 had terrible fuel mileage when I had first completed the swap. It would burn your eyes if you were standing anywhere near it. I added a heated 02 sensor and it helped a little. What really helped was when I found you needed to give 12 volts to the pcm for power steering input, pin C9. Once I did that it was 100 times better. It still runs a little rich but I think it's my exhaust setup and tuning.

Thanks for the links and info guys. I'm not sure what O2 I'm going with yet but I'll figure it out. Suggestions of ones that have worked well are always welcome.

As of right now the car is running, and pretty well I might add. Just like it was in the video I posted earlier. Looks like I just didn't add enough gas.

I now know for sure that the fuel gauge is reading off by a 1/4 tank. I'll have to drop the tank to fix that. I'll probably replace the pump when I do.

I did get the +12v to the power steering switch so I'm good there.

I just got a factory service manual today and have been reading it all day (hehe, I such a geek! I went right to the electrical section! ). This thing is a phone book.


On a side note I have everything I need to make the BCM (body control module) , ECC (electronic climate control), and FDC (fuel data center) work in a fiero. For those who don't know what these are, it is the system in these caddy's that basically works as a scanner. You can read codes, clear codes, take snapshots of sensor readouts while driving, get live sensor readouts (including RPM and speed), cycle PCM/BCM outputs and switches as a farily complete diagnostic tool. Rich/lean indicator or closed loop also. The list of things you can do with this setup is pretty amazing and I'm still learning more. I'll post a complete list once I get it all figured out.

Best of all the parts can be bought off of almost any 4.9 caddy. Total cost is very little. If I didn't have all the parts already It probably would only cost around 30 dollars total. I'll start a new thread when I start the actual build but I can tell you there is less then 10 additional wires total. Everything is electrical and I may be able to work in some aftermarket parts for fun. Maybe find a way to re-use the caddy keyless entry module. I'm very excited to get it working and figured some of you might be also.

I know some of you will think I'm crazy but I'm actually glad the mechanical part is almost over. I prefer the electrical side myself. Lets see if we can't use this luxury car stuff to its full potential. We have the alternators for it.

heated O2s are the best way to go if you dont have a catalytic converter. get them from the junkyard off a Northstar cadillac, dirt cheap...if you are running a catalytic converter, then use the stock GM denso O2 sensors. avoid using bosch O2s, as they require quite a bit more heat to activate, you would need a very restrictive cat. conv. to get them up to temp...

quote Originally posted by stickpony: heated O2s are the best way to go if you dont have a catalytic converter. get them from the junkyard off a Northstar cadillac, dirt cheap...if you are running a catalytic converter, then use the stock GM denso O2 sensors. avoid using bosch O2s, as they require quite a bit more heat to activate, you would need a very restrictive cat. conv. to get them up to temp...

I believe I'm running a GM sensor now. I'll have to double check. I also have a cat...


I wrapped everything from the manifolds to the cat after this pic was taken. I half expected it to work since the wrap would lock in more heat. But I'm still running rich. I'll probably have to play with it to get it right.

[This message has been edited by Fieroseverywhere (edited 04-27-2008).]

I figured I'd post the fix to my problem.


Its was low on gas but not out. We topped off the tank and the fuel pressure came back up. Still wasn't right. The O2 sensor turned out to be a bosch. I replaced it with a Delco and magically it stoped running as rich. I had to clean up the spark plugs at this point since most of they had fouled out. It fired right up and sounded much better. Still though, it wouldn't take any throttle. The idle had started hunting also.

I searched and searched to find the problem. I ended up unplugging the vaccume to the EGR valve. The idle immediately smoothed out. Hmmm. I plugged it back in and unplugged the connector to the EGR silonoid. Nothing. Got out my test light and found out that I had forgot to complete the circuit to the silonoid. I added the missing power wire and presto... runs almost perfect now. Still got some work to do to get it on the road officially but at least it runs like it should. I even got the test drive it up and down the street.

Just thought I'd finish up this thread with the explaination. If your 4.9 has a hunting idle and wont take throttle.... check your EGR silonoid. Later.

Did you buy a harness, or make your own? I am trying to build one now. The mechanical part is where I have fun. Electrical,,,,,not so much.

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1988 GT Wingless Fastback 5 Speed Purchased 8-4-07


1986 GT (Soon to be 4.9)
1992 Deville (Soon to NOT be 4.9)

Billiard Ball Shifters For Sale! https://www.fiero.nl/forum/Forum4/HTML/038696.html

quote Originally posted by Carver1: Did you buy a harness, or make your own? I am trying to build one now. The mechanical part is where I have fun. Electrical,,,,,not so much.

I made my own. Myself I prefer electrical over mechanical so I'm just starting to get to the fun part for me. I'm still taking notes along the way so I can post a breakdown of a 4.9 harness. Just need to get all issues worked out first.