Engine problems

[87GN87GN]

Hey guys, got an 87 GN with 90,000 miles. Car is completely stock and was running good but started having issues getting above 3000 RPM when on the road. Starts and runs fine and while in park or neutral will rev to 4000+RPM and accelerates normally but when on the road will not get above 3000 RPM and just kind of stops producing power as it gets around 3000. Turbo does spool some but it doesn't really add much kick and there is just an overall lack of power. Can get to around 50 MPH but that is it. Car has a new stock fuel pump and since trying to troubleshoot this issue have replaced ECM, chip, MAF, ignition module and coil pack. No change at all after replacing all these compenents.

Just got a Scanmaster and should have it installed this week and I know that will help me troubleshoot. Any thoughts on what this could be? Engine does not miss and runs smoothly but when it gets to around 3000 rpm does make a few pops as it flattens and stops making power. Help!

 

[TURBOELKY]

Are you having any valve train noise? I would take a guess and say your valve springs are worn, or cam is going flat on a lobe or 12. I would also check the turbo for up down/in out play. Thats a cheaper fix than an internal problem. I'm sure other members will have good info on what to look for too. Good luck man, hope you get it figured out and back on the road!

 

[No disintegrations]

Save all your old parts. They are likely still good. My first thought is the cat is clogged/melted. You can unbolt it at the down pipe, tie up the pipe and it should wake right up.

 

[EVIL]

Check for exhaust leaks too.

D

 

[Chuck Leeper]

Stock fuel pump. As in a 30 yo, 90K pump?
While you are installing the SM, add a fuel psi ga to the equipment list. Put it under the w/s wiper, and take a ride.
Could well be that the pump makes enuf flow/psi to support a 4k rev, [takes virtually no power to do so]. Same for low power driving.
The cat suggestion is also a good start.
While you are at it, do a spring cleaning....

 

[whitehot1]

The Spring Cleaning Guide is in the link below.

If you haven't done it already, it may help.

http://www.gnttype.org/maint/basics.htm

 

[87GN87GN]

Are you having any valve train noise? I would take a guess and say your valve springs are worn, or cam is going flat on a lobe or 12. I would also check the turbo for up down/in out play. Thats a cheaper fix than an internal problem. I'm sure other members will have good info on what to look for too. Good luck man, hope you get it figured out and back on the road!

Thanks for the reply. No valve train noise at all and car made good power up until this problem started first as an intermittent problem and now it is there all the time. Problem started about 4 weeks ago.

 

[87GN87GN]

No exhaust leaks and running a test pipe - no catalytic converter. The fuel pump is a new stock pump put in a few months ago and the car ran fine for at least 500 miles with it so I have been doubting it has gone bad and is only making "partial pressure" but as Chuck suggested, that could be the case. Think next step is the fuel pressure gauge and getting the scanmaster installed too. A fuel delivery issue is starting to look like it is the problem. Could the throttle body be bad or is there somewhere in the intake system that a partial block could develop?? I have not seen much mention of throttle bodies going bad on the forum but is that possible and what is are the failure modes when they do start to go bad?

Thanks for spring cleaning link too, that is a great link! I'm new to the forum and really appreciate the help guys.