Just got the z out of the paint booth and getting ready for a car cruise this Friday. I went for a test drive today and it stumbles a lot when holding the gas pedal steady at any rpm. Now I am searching and not a newbie to the z cars. I am on a dead line and would like this beautiful car running good and not just looking good lol. So here is what I have done. halve Egr delete still the the unit on the back of the engine but blocked off the tubes and vacuum lines and took out the solenoid. Carbon canister remove blocked all vacuum lines. Aiv system deleted. Changed to the new style injectors. New fuel filter. New ngk plugs. I have a check engine light and idel is at 1500 rpm. The car was sitting for 9 years due to a simple fuel injector issue anyway I fixed that and drained the old gas. Fired right up and idles great but when I slowly push the gas the rpm dips down then comes back up. Now if i hold it I cam hear that its stumbling while not under load. When I drive it its a lot more noticeable. I'm just needing some help here since I don't have a whole lot of time before I need to take her out and show her off. The stumble also happens at high rpms but happens more when letting off the gas or holding it at cruising speed. Any help would be greatly appreciated.

Thanks, Erik

 

Forgot to mention that I can not get the ecu to go into self diagnostic mode. Turned the ecu screw fully.clockwise wait 2-3 sec then turn fully counterclock wise and I get nothing no flashing red light or check engine. I have tried having the ignition in the on position or started and i get nothing. Also I can unplug the mass air and nothing happenes does not die or go into limp mode took a drive with it pluged in and not plugged in no difference. Stock air box

 

Power transistor was updated to the new one and I'm going to clean all the connectors and check voltage and ohms according to the repair manual. Also going to check timing tonight

 

Is the air filter clean?

 

Cleaned everything and then put the timing light on and it reads 0 degrees and I cam not adjust it any further than 0 so I'm thinking maybe the timing belt is not lined up correctly since I have read that can happen

 

Ok so my timing belt all lines up so am I reading the timing right it reads right on the 0 degree I'm using an inductive timing light hooked to the loop wire in front. I'm thinking its the crank angle sensor since this is a 90' I can get it to about 2 degrees that's it. Just wondering if I'm reading the mark right or should it read 0 degrees

 

I have the same problem exactly with mine, it starts to stumble when holding the gas pedal at any constant really annoying and and hard on the car to always be accelerating or decelerating with no happy in between! I also have a very strong smell of fuel entering my car not from exhaust. all my problems began after installed my cold air kit! Any suggestions i want to fix this motor up good so i can sell it and put the stage 6 long block in! so excited to have 1000hp!

 

Check your timing mine is off by 10 degrees. Also I smell fumes come into the cabin. I have black smoke coming out of the tail pipe when I floor it which meandering its running to rich which would explain the fumes. Since mine is a 90 I'm going to get a uses head from a newer model and get a new cas since I can not get my timing past 5 degrees

 

Not sure if anyone is really following this but the end result was a bad ecu, cas, and tps replaced all those and she runs great

 

Congrats man

 

Thanks for the Update..

But was it only one of them, or all three?..

Cap

 

My cas was shot could not get the timing to 15 degrees, the ecu would not let me into it either with the self or ob1 the timing now is fluctuating a bit and tested the tps and the volt are off a bit. But for sure it was the ecu and the cas

 

dude i think im having the same problem as you. Did it eventually choke out and you had to let it sit for a while before you could start it again?

 

Hey guys. I just done the TT swap into my 1990 about 2 months ago. The motor I have no clue what year it is, but it has the old style fuel injectors. I have the dual intake set up with z1 upgraded ecu. I replaced all of my spark plugs while it was out.

Just drove about 30 miles on it today in 95 degree weather and when I got off the interstate and came to a stop it started misfiring and the idle dropped. While driving it it first had a hesitation then progressively got worse. By the time I got in my driveway it was missing so bad I could hold the throttle to the floor and it would hesitate then shoot up to 3k then hesitate again then shoot up to redline. I noticed on my boost/vacuum gauge the vacuum was sitting at 15 when normally at 20 while at idle. I went to listen to the exhaust and it was sputtering on both sides. While driving it just before I got home going up a hill it would cut out and not accelerate at all then surge between having power and no power This should mean whatever is wrong controls both sides of the engine due to dual intake and dual exhaust (learned that when I had a bad fuel injector a few weeks ago. The exhaust only sputtered on one side while the other would sound perfect.) I do not have a timing light. This cas seems to sound like it could be my problem.

This was the same problem I was having with the NA motor just before I did the TT swap. My first thought today was a fuel pump going bad, but the cas sounds like something to think about.

If anyone thinks this is a different problem please share your opinion.

Edit: When you say cas are you talking about cam angle sensor or crank angle sensor?

 

Well I let the car sit for about an hour and a half and started it up and it idled perfect. Drove it to church and back and it ran great. I see a possible problem in the future though.

 

The Book calls it the Crank Angle Sensor.. But it's Located on the Front of the Exhaust Cam.. to it is actually a Cam Angle Sensor. Makes not real difference, as you only have one.. and it's a CAS..

Do you have the Transistor Driver pack from the Other Engine .. Located on the Cam Belt Cover Right Side? Could be that the Driver Pack is having Heat Issues?..

If it's the Same problem before and After the Motor Swap.. did that Transistor Pack stay with the Car or the Engine?..

Cap

 

The old motor is gone to the scrap yard. I don't think it's a common problem because I've had the motor in for 2 months, 4,000 miles and took a trip from TN to KY back to another part of TN then back to KY then back home to TN and it didn't do it.

 

i have replaced fuel filter and cleaned terminals to fuel injectors all ohms read between 10 and 13 on all six, 4 sit about 12ohms and the back two are about 13ohms? cleaned maf and chk filters all seem fine?

 

You don't need to go spamming your problem everywhere, you already started a thread for it. Maybe you should check out how to use the question mark properly too

 

Well car is starting to have this problem more often.

Took a trip to KY last week and about 3/4 of the way there it started having the sputtering problem going up and down the mountain. It eventually straightened back up. Didn't drive the car while I was there for 4 days. While on my way back home it started missing while under load and at idle. Stopped and ate and 30 minutes later I started it back up and it got me the rest of the way home and started acting up again about 20 minutes from the house. Got it home and let it sit over night and it ran fine the next day.

The best I can explain what it is doing is...With engine warm at idle it sounds like it is misfiring on both sides of the engine and rpm's are sitting anywhere from 900-1100. I can rev it up to 2k rpm's and let off of it and it will sometimes settle at 1500 rpm's and idle smoothly. Most of the time it will go back to misfiring and idling at 900-1100 rpm's. When it hasn't ran much that day it will accelerate with no problem. When it has been ran a lot that day it will eventually get to where I will give it throttle and it will bog down and not accelerate at all. I'll let it sit for 30 minutes and it will run fine for about an hour and go back to bogging down again. Also it runs very rich. Enough to paint my rear bumper black and grey in a weeks time. Boost only shows to be running 8 psi on the aftermarket gauge. I know it's suppose to be running 9.5-10 psi. I've checked all my clamps and vacuum lines and have no boost leaks.

I'm hung between either the PTU or the CAS. I'm going to try to get a timing light and check the timing, but will this show anything if it's running right at the time?

Any thoughts, ideas or experience with this problem would be greatly appreciated.

 

Well ive decided to replace the PTU. I ordered it yesterday and it should be here sometime next week. This motor has the S1 PTU so it needs to be replaced anyways. I'm hoping this will do the trick.