I bought this car from a dealer. It did not run at the time I bought it. I got it running on six of the eight cylinders, and finally on all eight. Now it will not idle correctly. When I first start the car it will not stay running with out my foot on the gas a bit. About a minute later it will idle but it idles rough and the rpms just jump around. Sometimes they climb to almost 2700 rpm, without me giving it any gas. And sometimes when I give it gas, it acts like its choking out. I really have no idea what the issue is, so if anyone has any ideas, I could really use the help. Thanks.

 

Check your TPS voltage, make sure your vacuum lines are hooked up, make sure the IAC is clean, just a little dirt can cause that to go crazy, same with the MAF. Just pretty much make sure all the sensors are functioning, if you can get ahold of a snap on computer or something that would be best. Run some injectors cleaner through it. Has it had a tune up? Specificly the ignition module.

 

I keep getting a low voltage to the TPS code. So I replaced the TPS and tested the old one, it was grounding out inside the sensor. I still get the code but I never cleared the code out of the system. The MAF sensor is new, I originally thought that was my problem, so I spent like 300 bucks on that. I need to check the IAC, which I'm going to try and do today. And when it was only running on six of the eight cylinders, it was because of clogged injectors and build up in the fuel rail. It probably needs new injectors. It has not had a tune up. I don't drive the car yet, I haven't drove the car since I've owned it. A couple of my vacuum lines probably need replaced.

 

Well than I suggest just check over everything a couple times, give it a good tune up, drive it as much as you can, try to get it cleared out. It just needs some TLC. If you end up needing new injectors I have some stock 19lb injectors from my 305 I just pulled. They're all good, just let me know if your interested. Good luck.

 

Well thanks for your help. How much would you want for them injectors?

 

I paid $50 for them back in september I think, I put maybe 600 miles at the most on them before the blow-by got real bad so I pulled the 305 in favor of a 355. I'll let them go for $40 including shipping if you decide your interested. Have pics and part numbers to.

 

Alright, can you email me the pics and part numbers?

 

It could be the mass air sensor,my car did that without it.

 

I had pretty much indentical issues. Car would cold start at 400 RPM and die. Two or three tries to start it and it would idle roughly at 1000 RPM. Drive a few blocks and once the engine is warm, it wouldn't want to go less than 1800 RPM. "Standing" on the brake pedal at stop lights. Let the brake go and car would take off on it's own, shift into 2nd. No feet on any pedals.

Here is the deal.

TPS voltage read .550 idle and 4.5 volts at WOT. (at the TPS sensor)

But the ECM box was reading the TPS at .980 volts at idle and 1.2 volts at WOT. This would explain the high idle and also why it would feel like a choke was on at low to low-mid throttle going down the street.

Got another ECM that read the TPS voltages properly. But it wouldnt' fire the injectors (no start). Exchanged that for another ECM box.

Smooooooth running now. Starts up at around 1200 RPM then 5 seconds later bounces back down to 700 or so. Once it's warmed up, it idles at 600 RPM. Everything is smooth and steady going down the road.

 

What kind of ECM did have to buy to fix the problem?

 

Just a regular AC Delco box. Take the chip out of your old one. Put it in the new box. Hook it up.

(The first replacement was simply defective)

 

Ok About how much do those things cost?

 

RockAuto.com has them for $75-105. Coupon codes are in the Aftermarket Vendor review forum.

 

How hard are those things to replace?

 

Have you ever changed your chip?

The hardest part is kneeling/sitting down with your passenger door open and removing the 4 or so screws underneath the dash. Once the lower panel comes off (the thin piece that has the footwell light), you'll see a silver box up there. Sort of behind the dash pouch area. 2 more screws to unbolt it. Then it slides down.

It has a "clothes pin" type connector that releases the ECM box. (disconnect the battery before unplugging the ECM box)

Once the box is unplugged, the new one simply plugs in, then goes back up into the same spot you removed the old one. You'll need to remove your computer chip from the old box (there is a small rectangular access hatch on the box where your chip will be) and put the chip in the new box.

Figure on 20 minutes give or take.

I've had that box out before to change chips in the past. This time my mechanic figured out it was the ECM box. He tested all the wiring in there and then concluded it was the ECM box that needed replacing. And it works like a new car now.