SystemX

What's Wrong With My Car??!!!!!! OK. Here's what I've got. An 89 Trans Am GTA 5.7L L98 TPI. I just picked up this car a few weeks ago. It was experiencing what appeared to be a fuel starving issue. It would start and idle fine but would bog down and want to die out at about 2500 RPM. It was under the suspicion of the seller that it had a bad fuel pump. No problem, I've changed TA fuel pumps before. I changed the fuel pump, strainer, sending unit and filter and ended up with virtually no change. Upon further study it was found that it seems to be a rich fuel condition not a fuel starving condition. I have posted two videos of what the car runs like including run through of engine diagnostic information using an old Tech 1 unit. The videos can be seen here: Vid 1: http://www.youtube.com/watch?v=co37SWAZx7s Vid 2: http://www.youtube.com/watch?v=jc-WwIkn4Ko Video 1 is the car startup and open loop condition, video 2 is closed loop. There is virtually no difference in how the car runs just wanted to be thourough. Also, I apologize for the poor video quality. Here's everything else I've done to the car: -replaced spark plugs -had ignition module tested (twice) good both times. -checked EST circuits - all fine -checked fuel pressure - 42 PSI base and goes up with throttle -checked for vacuum leaks - none that I can see -checked coolant temperature sensor - reading normal Since doing all of the above and running and testing the outcome I seem to have succeeded in only getting worse. I'm now hard pressed to get 1000 RPM out of the car. If anyone has any ideas, any at all, I would greatly appreciate hearing them. Oh, and before I forget, I just wanted to note that I have NO error codes! That's right, NO error codes. hmmm Thank you all! I appreciate any and all help with this one!

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89 GTA Trans Am

Viprklr

Your IAC should not be pretty much pegged at 160 the whole time. Use the reset procedure found in the tech articles at this site's homepage.
You should have counts around 10-20 at full hot idle.
Replace your O2 sensor. 4mv? Didn't know that was even possible. This should fix your fueling cell 0 issue.

Give that a shot and let us know what happens.

Vader

Welcome Aboard!

There's not much better than a good game. Can I play?

First, congratulations for supplying the quality and quantity of information you have. Too often we see threads containing "My car won't fire - What's wrong. It has new plugs."

The first video has audio which is a bit alarming. Understanding that some video devices have marginal audio support, it's difficult to determine what's going on. Is there a loud hissing while the engine is running, or is that just normal mechanical noise being picked up by a sensitive microphone?

I noticed the IAC counts are fairly high, indicative of a minor problem. The BLM and integrator are at 120, EST looks normal with no knock counts and advance at 15º, TPS looks good, O² looks normal for a cold startup, EGR is off, load value looks normal for idle, MAF looks right, CTS and MAT look right. In short, it should be running just fine.

Once it hit closed loop, the idle dropped according to temperature, the injector pulse looks decent, the O² is showing some activity and is crossing the bias point, and MAF looks right. I did notice the TPS voltage take an excursion to over 1V at some point. Did you "blip" the throttle to maintain RPM? The IAC counts were also wandering, often hitting the ceiling at 160.

The throttle minimum air, IAC passages, and possibly the PCV should be checked out to see why the IAC counts are so high. Not having enough idle air could be a big part of the problem, and could be causing the O² to read rich as it appears to be.

SystemX

Thanks for your responses. Gives me a couple more ideas to look at.

A couple things I forgot to mention:

1. I am blipping the throttle in a few places just to show the response on the Tech 1 i.e. TPS voltage climbs etc.

2. Since making the videos I did replace the O2 sensor with no effect on performance.

3. I checked compression and have solid compression on all 8 cylinders.



I'm going to take a look at the few things mentioned and see if it gets me anywhere. I'm still open to any ideas. Thanks for all the good advice!

Vader

I was thinking that the O² readings were the result of a mixture issue, and not that the O² was faulty. It seemed to report reasonable numbers when cold and did produce crosscounts.

I'd still look at the throttle body and its parts, potential vacuum leaks, and injector/FPR leakage.

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Later,
Vader
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"Everything should be made as simple as possible, and not one step simpler."

SystemX

Update...

So I removed the throttle body and cleaned it all out. I removed the IAC and cleand it up as well. pretty well caked with carbon as to be expected. I re-assembled everything and let her warm up and my IAC counts dropped to the 40-50 range instead of being pegged at 160 and I could rev it to almost 2000 RPM.

Next I went throught the proceedure to set the idle minimum air from here:

http://www.thirdgen.org/tpimod2

and got it dialed in perfect at exactly 600 RPM at warm idle in Drive.

re-connected the IAC and it's backed to being pegged at 160 and I can't give it any throttle at all.

Could the IAC just be sticking? Should I replace it? let me know if any of you have any ideas.

Thanks again and stay tuned for our lightning round!

rgarcia63

You might try disabling the ECM timing control before doing the procedure, timing needs to be static for idle adjustment.

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88' IROCZ 388/6.4L TPI Motown 350/4-bolt main stoker, and then some.

driver101

i had the same problem turn out to be bad injectors. mine would idle rich but little throttle response or would die i replaced the injectors,now it runs awesome

SystemX

Thank you all for the responses. Still not there yet but still trying.

In regards to the timing, I did diasble the EST and set the base timing to zero.

As far as injectors, I'm pretty much at the point of throwing money at the thing to try to figure it out and injectors is the first thing on my list. I got the tip on fuelinjectorconnection.com from another post on this site. I'm probably going to take a break from it before I start doing that while I work on my mini-Firebird (otherwise known as a Fiero).

Keep the ideas coming and I'll keep you all updated.

Thanks again and stay tuned!

83Firebird420

*runs down to the stage, yelling, arms flailing high fiveing random people*

lol anyways

i once experienced this problem where at 3500rpm it would just stop reving, almost thro you forward the stop in acceleration was so abrupt. like a rev limiter (without the satisfiying noises). turns out my cat was completely plugged. if you dont need ur cat where you live it might not hurt to empty it out.

SystemX

And the winner is... Driver101!!! Congratulations. You win a years supply of Rice-A-Roni the San Francisco treat!

All kidding aside... I got home from work today and cut off my catalytic converters. No difference except for loudness. Sounds pretty bad-*** actually!

My brother-in-law who is a mechanic came by later to check it out. He's moving back into town from the west side of the state. After about 5 minutes of looking at it and breaking out my test light he found that the injectors on cylinders 1, 2, and 8 are just dumping fuel in the cylinder. So much that those cylinders wont even fire. So, I'm on my way to fuelinjectorconnection.com to order me some new injectors.

Thank you all for playing. All of your help is greatly appreciated. I'm sure I'll be back with more challenges just hopefully not in the too near future.

Thanks again! -Chris