Ever since I had some work done on my Z by a local shop, (replaced fuel lines and water hoses) I have had problems with the engine. I have resolved all of them except for the stumbling and surging on acceleration when the engine is cold.

The stumbling goes away once the engine reaches operating temp... but the surging remains. I re-set the timing which was off, cleaned the air filter, checked the mass air flow for dirt, and cleaned the contacts on the water temp sending unit.

I know it is impossible for anyone to say what the problem is, but can someone just suggest a most likely component that may be at fault?

The car is a '90 N/A auto, well maintained, has 120,000 miles, new plugs, and ran perfect before the repairs were made.

If I can't figure this out, I'll have to start replacing parts such as the o2 sensors and all the other components which might be at fault. I'm self-employed... and with the economy like it is, I really can't afford to just start replacing parts when I don't know if they are defective or not.

Any help is greatly appreciated!
Thanks
Johnn B
visions2001@att.net

 

have you checked your ECU codes yet?

 

Thanks for your reply. I haven't checked the ECU for problem codes. I don't know the procedure. I have heard there's a way to do it without a scanner.

If this is possible, can you give me the procedure on how to do this? Also, There are (2) sensors right next to one another on the front of the engine. I know one is the water Temp sender, but what is the other one?

Thanks for any help!
JohannB
visions2001@att.net

 

yay for search!!

https://www.zdriver.com/forums/showt...ight=ecu+codes

 

Thank you for the link. I'll give the ECU diagnostics a try and see if anything comes up. I haven't had the 'Check engine light' to come on, but I'm not sure if any of the possible malfunctions I have would activate the light or not.

Thank you for your help!
JohannB

 

have you tried adjusting your throttle position sensor?

if it is advanced it will tell your injectors to increase fuel which is unnessary for the rpm temp etc.
by adding that unneeded fuel you lower the stoichio metric range and "choke your motor" for easier terms.

 

Thanks for your suggestion. I haven't tried adjusting the TPS, but I may give that a try too. When I first got the car. it was doing something very similar... and eventually I found out the TPS was bad, and I had to replace it.

Thanks for your help!
JohannB