Just went through and fully rebuilt the engine in my 89 Iroc-z 5.7L. I got everything back together and it fired right up, it was running fine, the thermostat opened, all was well. I shut it off, turned the A/C on to make sure the cooling fans were working, tried to start it and it refused to stay running. It started backfiring through the intake and running poorly. The tach was pegged at 7K at all times when it was working fine before. I changed out the ignition module because I had cracked it while installing the engine. The tach started working right, but the engine is still running like crap.

I have 40PSI of fuel pressure at the rail. Plugs, wires, cap and rotor are all new. Rotating the dizzy doesn't have much effect on it running. Any ideas?

Edit:

Finally fixed it. It was the mass air flow sensor. Car is running great.

 

Check the dizzy connectors and spark plug wires firing order.

 

All of that is correct. My uncle gave me an idea, the valves may be too tight.

 

the pick up coil may be damage inside the dizzy. I believe that your issue is with the ignition.

 

Could be. The thing thats throwing me is that it fired up and ran great for the first 15 minutes. My uncle is sharp with 350's considering that he has built a few hundred of them, so I will check the valves first, then move on from there.

 

If the valves were too tight it would have ran like crap from the start.

As mentioned, I think it is ignition related.

 

Ok, valves are fine. Here is the weird part, it will run only if I advance the ignition WAY up. I set it to TDC, then turned the dizzy to point at the no.1 plug wire. Wouldn't start at all, not even try to start. So I rotated the dizzy counter clockwise, which should be advancing the ignition, all the way around to where the rotor is damn near pointing at the no.8 wire and it starts, but backfires through the intake.

So, if my logic is right, something is advancing the living crap out of the ignition right?

 

If u rotate the dizzy counter clockwise from #1 to #8 then your turning almost a full 380*. So why dont you just go clockwise which would be 1/8th of a turn, rather than 7/8ths of a turn? Im not doughting your uncle, but we are human and we do mistakes. Did you line up the timing marks on the sprockets for the timing chain? Did you verify that when you lined up the timing marks, that your on the compression stroke TDC for piston #1 ? If your timing marks are not lined up, then you WILL run into problems. Last year we did a cam change in my IROC. We did everything right, so I thought. After experiencing all the vacuum lines being blown off from backfiring out the intake, a buddy of mine (member of this board "Chevy8588") told me that my dizzy was 180* out. So I loosened up my dizzy, lifted the dizzy 1 inch, turned the rotor 180*, dropped it, and VVVRRRROOOOOMMMMMM.. Turned on without a hitch.

 

Let me ask you something. Depending on where the issue lies, the ECM should be recording error logs. Have you jumped terminals A & B in the ALDL port? If there is a timing issue and your timing is indeed correct, then possibly your ESC Module is bad or the EST module. But please note down the TC's so that we can try to narrow this down.

 

Definitely right. I double checked his work on the timing sprockets. When you loosen off on the dizzy, you can turn it either clockwise or counter clockwise. I didn't go for a full rotation, I just turned it maybe 1/4 turn to advance it.

I just grounded those and I have to test it, but now the damned starter is acting up. Will post back with the results later.

 

It's possible you may have a vacuum leak. Spray something like carb cleaner on the areas that bolt together. If the RPMs go up then you have found the problem.

 

The obvious part is that you have a backfire through the intake so either one or some of your intake valves are not closed at time of ignition. It could be that the ignition is off or one or more of the valves is not closed. At this point if you checked timing I would do a cylinder leak down test on all cylinders. Make sure the valves are closed when testing.

Also did you rebuild the heads or change the cam?

 

Well, we have been narrowed it down. The battery was shorted out, causing the starter to act up. Grounded out the A and B pin on the ALDL and viola, it's fired right up, no backfiring, etc. So, I am thinking that the battery shorted out the ESC.

 

i wouldnt go cruising with A & B terminals being grounded. While the 2 are grounded and the Camaro on, It is called "Field Service Mode." It is not recommended to drive erratic. Only for diagnosing. Here is where I can verify my claim.

 

Oh, I will be fixing it, I just needed to know if I was looking in the proper direction. This is a 2 owner, numbers matching, 115K mile, fully loaded specimen of an IROC-Z. I even have the original build sheet from the factory. I am slowly restoring it to factory condition, it will be done right, or not at all.

 

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I'm with you on that one. I just ordered a butch of hard to find interior pieces from various internet stores to get my IROC in its original form.

 

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Code 44 is the O2 Sensor. I believe you meant a Code 33 or 34. Also the ECM doesnt learn from "Sensors'" rather a sensor, The VSS, or Vehicle Speed Sensor. Dont remember where I read it from but it was from a well known source.

 

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HAHA. I remember you now. I thought your member id sounded familiar. Well I learned from trial and error. Plus I picked up a book (below). Has lots of good info. Yeah man, Ima take a picture of how my bad pickup coil looked when I took it out of the dizzy. It was shattered! Hey man thanks for the complimants. Im flattered. No VSS? HMMM. Well then. You got me on that one bro.

 

So, I am almost stumped here. Changed out the ESC with a known working one from my 90 5.7L Silverado, no effect. I unplugged the knock sensor, no effect. Just disconnecting the EST wire to the ECM, no effect. It will only run with the A and B terminal grounded on the ALDL... So, I think that I can rule out the pickup coil since it runs fine with the ALDL grounded. I am down to the ECM. Anything to check before I take that plunge?

 

Here is a crappy quality video of it, but it gives you an idea. I will borrow my sisters camera and get a higher quality video. It's only 4MB, so it's slow internet friendly.

http://www.youtube.com/watch?v=SdhmqVn1_jE

 

bad ecm or lets not forget when you jumper a and b you provide ecm with a ground .check your grounds.ive also seen a weak signal from pick up coil in dizzy do this...when you jumper a and b this puts ecm into set timing mode and runs directly off of icm.

 

hey when you turn the key to on is there a check engine light that flashes before you start it? check you vacuum lines with a vacpump hand. check the vacuum to the fuel vapor canister, fuel pressure regulator, brake booster, usually there a vacuum reservoir in the fender by the powergear. do you got emissions? egr solenoid, vacuum lines to the tb, theres a vacuum line under the dash for the tcc switch on the brake pedal..the alarm is messing with it, pull the alarm fuse. pull your dizzy and check the tooth alignment, could be off a tooth

 

yeah. take youre "bad" ECM and put in the silverado. Make sure to swap out the MemCal so that you can also verify whether the MemCal is bad.

 

i fried my mempak and cal pak, while back

 

I would try to veriefy youre claim on this one. In my 86 I have the EST pigtail above my blower motor. I dont need to have A+B jumper to set my 6* timing. But Im not too familiar about the 89 ECM. IIRC, the 89 is when a few things changed such as the 9th injector aswell as a few other things.

 

AHHHh, that suxs bro. I fried my Hypertech Thermo Master PROM about 10 months ago. So I got a Moates G1 adapter and a buddy programmed a EPROM for a 87 350 BIN file. So once I got the new EPROM, I connected my 305 MemCal to the G1 adapter which bypasses the 305 PROM but uses the CalPack and allows to use the 350 EPROM.

 

i was just reading the haynes manual, on page 6-3 bottom right, its talks about how to enter ecm's stored codes, then it say,"note:do not start the engine with the diagnostic terminal ground" and on page 6-7 -->to test the Prom "start the engine, then enter the diagnostic terminal by grounding the A b..and there shouldnt be a check engine light, but if there is. turn off the car then test for codes if it 51 then your prom is bad or installed backward, but if its installed backwards it bad anyways.."

i just curious how youre able to get an idle, try dissonect the timing wire will it idle.. tps adjusted? did you do the minuim idle air adjust on the tb? it includes on page 4B-16in haynes middle section) heres a picture

 

Yeah, I have a code 12 and a code 42, the code 42 comes from the timing wire being disconnected.

Good idea, nice to have a running test subject.

My 89 FSM says to ground the A and B to set the timing, or to disconnect the EST wire.

My Factory Service manual says to ground it and start it to set the timing. No code 51 in the system. It won't idle with just the timing wire disconnected. Haven't tried adjusting the TPS or the IAC yet, I will look into it.

 

if it wont idle with timing wire disconnect,,, whats the timing mine 6*btdc with timing wire disconnected, no grounding needed

 

I got a good source for tuning the TPI System. This is a link for the High Performance Pontiac. But the TPI is the same for Pontaic and Chevy. Here it is ( http://www.highperformancepontiac.co...gta/index.html ).
And here is another source ( http://mpikas.blogspot.com/2008/08/t...june-2000.html ).

 

Ok, I have news. I took the ECM out of the IROC and put it in the Silverado. Wouldn't start it at all, so I figured it was shot. Bought a new one, used my old Prom chip, slapped it in the IROC and it still wouldn't run. Next I pulled the dizzy and changed out the pickup coil, the dizzy looked off by a tooth, so I spun the oil shaft and slapped the dizzy back in. Again, wouldn't run right. Grounded the ALDL and it still runs fine, so I set the base timing and it's locked in, but it still won't run with the ECM controlling it.

ANY ideas would be helpful, I am down to the PROM chip.

 

Sorry to hear that bro. Maby Ignition Control Module, Spark Control Module?

 

when you turn the key in the ignition to on position, do you see the check light light flash and stay on?

 

Replaced the ICM and tested the ESC with a known working one.

Think so. Why?

 

FINALLY tracked this SOB down. Mass Air Flow sensor.

 

REALLY!!! Another 3rd gen ready for the road. I'm suprised that the ECM didn't throw a code 33. Good job man!

 

Yeah, I agree that it's odd on no code 33, which is why I never really thought of it. When you have changed the ECM, Memcal, EST, ESC, pickup coil, ignition coil, cap, rotor, plugs and wires, you tend to HAVE to think outside the box.

 

Atleast u got all that out of the way. Think of it as a major tune up bro.

 

did you put your cam in right!

 

Yeah. It's fixed now. It was the MAF.

 

maf? what brand you pick up.

 

A1 Cardone, which is a remanufactured Bosch unit.