I recently tuned my TPI setup, set the TPS & IAC, made sure the timing is ok (set at 8 degrees). The problem is when starting the car it will either act of two ways: It will idle at 1600 RPMs or sometimes even a bit higher, or it will behave normally and idle in park around 800 RPM and in gear around 600 RPM. It seems to run at the higher idle when cold but I have re-started the car warm and had it run at the higher RPM. Another funny thing is that however the car starts and idles is how it will stay as long as the car is running. Driving for 20-30 minutes won't kick it back down at all and vice versa. It seems however it starts up is how it will be until turned off. It does either or about 50/50. I can only think its either because my PROM has the cold start deleted so its dumping too much fuel in, or because it takes 2-3 cranks when cold it idles high to adjust for more fuel and stays there for some reason.

Anyone have any ideas? It gets annoying being at a stop light and idleing at about 1200 RPM in gear. The car does set a code 44, O2 sensor, occassionally. This is a 87' MAF setup too.

 

Anyone? Bueller?

 

May I give you a bit of advise please? The best thing I did for trouble-shooting is to make a computer to ALDL cable and download the free winaldl software. You can buy a cable if you want also. This will then tell you if the O2 sensor is working, what the IAC stepper motor is doing, what voltage the TPS is at, if going in close loop and a BUNCH of other stuff. If you have a laptop and $50-$75.00 for a cable you can find-out SO much in just a few minutes. BEST thing I ever got/made!!!!!! Could be your IAC, possable injector. Check with ohm meter to see that the coils are all the same. I had 6 out of 8 bad and my car did same thing. Wouldn't idle right/rough. High/low idle etc... Also clean throttlebody passages. With the computer set-up you WILL know what is going on without buying parts and hoping it fixes the problem. Alot of info in the prom burning section. If you like your car and plan on fixing it yourself, this is a MUST have item. BTW, when I first swapped my 305 for a 350, I didn't have the O2 sensor plugged in. When I started the car, it would bog out until it warmed up, but the idle was fine. But that was my car/experience. Yours may act different. I think the O2 sensor only makes small adjustments in fuel when out of idle mode. It shouldn't affect the idle speed. Was the problem there before the tune-up or is that why you did the tune-up? Could also be the wire to the IAC is intermitant. Make sure the MAF is plugged in good, check intake clamps,etc...I think a vacume leak wouldn't stay the whole time the motor is on and change from day to day. It sounds like a ECM thing because once it's high, it stays high and vice-versa. You need to check the things that the ECM connects to IMO. I'll keep an eye out on this post and see what happens. In the mean time, really think about getting the cable/computer thing. I promise it'll be the best money you ever spent on your car!!! Sorry for Rambling on

 

You set the IAC, but did you clean it's pintle? Also, make sure nothing is binding the throttle cable, and keeping it slightly stuck in an open position at times....

 

Yep!!! Forgot the obvious!!! Streetleathal is right on!!! When I first got my car many years ago, The throttle would stay open like he said. Just push back on throttlebody and see if goes back down when high. That makes the most sence!

 

Thanks for the replies.

To start off, I don't have a laptop, unfortunately. I do wish to get a cheap one even partially for this reason alone. I do have a decent ScanTool which reads data as the car is running, probably not as nice as the laptop and software but it gives vital info that can probably help me out.

Back story for the car is this: Its a 87' Monte LS that I converted to TPI back in the winter of 02'/03'. It was a bone stock 305 LG4 car....I used a 87' Trans Am, parting it out, for the complete TPI setup, wiring, etc. Got the car running in late spring of 03' and everything seemed "ok" although not enough power. I swapped in a mild 350 in the summer of 06' and then more problems began. It has vortec heads and a very reputable member here (won't say his name so people don't bug him) offered to burn me the PROM for the swap. Just some little changes for the 350 and eliminated the cold start injector and EGR. Car would be very hard starting and not hold an idle until warmed up. At the time of the swap I swapped on a 89-92 plenum and runners to make up for the cold start delete. Well fast forward to this spring when I've had it with the car taking 1 minute or so to keep an idle when cold and taking 5-8 cranking sessions to get started. First I swappd on a adjustable fuel pressure regulator. Found my stocker was leaking, which made sense for the very hard starting and that it seemed a bit light in the pants when WOT. Pressure is set at 43-44psi now. Car starts easier but still can't hold an idle. Hmm. I find out the throttle body is different for a 89-92 as well....supposedly the older 85-88 works with the 89-92 but the IAC passages are different. That and the fact my throttle body adjusting screw is busted (used a nut on the outside for adjusting) I got a 89-92 TB and throttle cable to go with it. Swap it on and viola, the car holds an idle great. Just too high. So I re-set the battery, I did infact take out the IAC, make sure its working properly and clean it out with the passageway too. Checked the timing, set at 8 degrees, got the TPS set (had to swap on the adjustable one of course) and set the IAC following the steps, nothing new. Car runs great. Start it up the next day, runs great. Wait a couple days and when cold it usually holds a very high idle which is where I am at now. The fact it doesn't adjust with driving or time makes me wonder why the ECM is keeping the idle high certain times and how it "should be" others. I think its when the car is cold it still takes maybe 2 cranks to get going, it might be adjusting itself to burn the more fuel and for some reason stays that way until the car is re-started.

I'll check the throttle, I did spray the linkage with WD-40, checked the blades inside, everything checks out ok. I'll double check when the idle is staying at 1600 RPM to see if the throttle is off the adjusting screw. I don't think it is. The injector idea might make sense too...

 

When you used the 87 Trans-am for the "Doner", you changed the ECM and have the 1227165, right? So when you had the prom burned, did you mention you eliminated the cold start injector and the EGR? Why did you eliminate the EGR? Was it the cost of the parts? Just from reading around here quite abit, the EGR system is something that is VERY important in the operation of the engine. It definately affects the performance and quality of operation. Do some searching about "EGR" and see what comes up. BTW, the prom has to be set for "no cold start injector". It will dump extra fuel through all of the injectors when cold. The Temp. sensor could be intermitant or the wiring/connector getting "funny". The laptop/software would be great in this situation. You said you do have a scan tool. What info does it give you? What's the Manufacturer and model # of the scan tool? Do you have a voltmeter that also measures resistance so you can check the injector's coil for resistance? I think you may have bad injectors or the prom was burned without the guy knowing the correct set-up. Also a bad O2 sensor will "lean-out" the engine when running above idle. Did you ever try starting fluid? If it starts right up then obviously starving for fuel. That's what mine did. Sometimes it would be fine/normal. Others it would be hard to start. Also rough idle. It had 6 bad injectors/coils. Anyway, first check the injector coils,find out about the prom, Think about restoring EGR system and check-out/replace O2 sensor.

 

The EGR was deleted because I used Vortec heads on the 350 swap and didn't want to start welding my $500 coated headers especially considering I very well could change heads down the road. I understand it doesn't neccissarily hurt anything, I am under the impression removing it doesn't really hurt either besides emissions.

I'll grab info from the scantool, it was the kind sold at Autozone IIRC, I have had it now for 5-6 years. Has a cartridge for 84(?) through 95' GM's.

The ECM is the unit from the 87' TA, correct.

I still believe the PROM was burned correctly but of course can't really verify that. I suppose I could PM him on here and see if he remembers anything from it.

I have a cheapie multimeter, I will look into checking the injectors for resistance. I never really mastered checking electrical/wiring with it though so I might need some help knowing what to set it at, etc. The idle isn't rough by any means just way too high on cold starts. I've had someone else also mention the idea of lowering the pressure down a bit since I have 24lb Ford injectors and its just a mild 350, perhaps my setting of 43-44 psi with the vac hose disconnected is a bit too high.

 

Ford injectors????? That's GOOD!!!!!, O.K. The multimeter thing.. You know when you put the leads together and it beeps or reads "0.00" or there about? That is what you need. First, do you have a digital meter or a needle that sweeps across? The coils should be 14-16 ohms. That is almost a short circuit/very low resistance. Look for the ohms button or turn the dial to that. "look like the letter U upside down" If it auto ranges then you're all set. You are measuring for 16 ohms, so you'd want to set the meter for more than what your measuring, like 20 or 200. Then the meter will say 15.7 for example. It don't have to be exact. As long as they are close to each other, that's fine. I had 1 that was 2 ohms and another 28 ohms. That's bad. BTW, I was thinking,The high idle may also be in the IAC circuit. if you jumper the aldl connectors A and B like when you do the code retreval thing, the idle will go up in that mode. If it don't, then the problem is in the IAC circuit. You should hear the motor/pintle/IAC operating. You can do it with motor off and have someone short the aldl while you listen at the throttle body, or you can start the car and see if the idle differs. Just a thought.