I have been fighting a problem for over a year with my car not pulling past 4,500 rpms. It's gradually losing power past 4,000, and it just will not go past 4,500 at all like it hits a rev limiter. I got a pressure gauge and everything seemed fine: With the regulator unplugged (but I did not seal those vacuum lines;I don't know if that matters) it read 50 cruising around and about 47-49 (mostly 49) when floored. So does this mean I am getting plenty of fuel? I did not test it under load with the regulator plugged in, but at idle it was at about 42. Any ideas????? I will have to rent or borrow a diagnostic sytem (I guess Diacom?), if you guys can't help me. Is there anything else I can check? I know there is something wrong, so don't tell me the TPI design will not flow past 4,500 rpms. I have heard of STOCK TPI cars pulling to 5,000. With intake and exhaust it should pull to there even easier, right? PLEASE someone give me some ideas, this is driving me crazy.

Thanks,
Jonathan

 

I'm thinking either bad valve springs, bad ignition component, or maybe even a clogged catalytic converter.

 

I will try an ignition module tomorrow since they are not that difficult or expensive. Any other ideas? I will post results if this helps. Thanks.

 

It could very well be the valve springs

 

How hard are springs to install??? I wish I would have known this while I was doing my intake....everything was torn apart. How do I know which springs to get???
Thanks for the ideas guys.

 

I tried a new ignition module today, and it seems to have better throttle response and a smoother idle, but NO improvement in the loss of high rpm power............

Jonathan

 

Are you still running the stock 22lb injectors? If so have you had then cleaned lately?

 

Yeah I sent the injectors to Cruzin about two months ago for cleaning/flowmatching. Any other thoughts????

 

First off, how many miles on the engine?

 

The valve springs are under the valve cover gaskets. It is possible to change them on a car, and if you do a search on this board you will find how to do that. You can call Summit or Jegs and talk to a tech. They should be able to get you a good set of valve springs that will drop right in. It is a bit of work to do the job, but usually on a higher mileage engine it's worth it.

 

The valve springs are easy to change. Remove all the spark plugs and valve covers. Do one cylinder, one spring at a time. Fill the cylinder through the spark plug hole with compressed air, use a spring compressor and remover the keepers, and the spring/retainer assemble will come off. Change all the valve seals while the springs are off. Make sure you get new retainers with your new springs as the factory ones are heavy and crappy design.

If you need more help with it, PM me. But before you go and do the sprins which may not be needed, we need to know how many miles are on the engine.

 

Thanks for the replies.
My car has 140,000 plus on it. The previous owner said the owner before him had the engine rebuilt around 90k, but there were no papers for it, so I don't know. I guess if it was rebuilt there is no telling what was put in it...
I was reading in an old service book my Dad has, and it doesn't seem that difficult to change out springs. But the spring compressor is like 100 bucks. I will call Autozone or Advanced and see if they rent one out. I wish I had the money for roller rockers right now. That would be convenient. What are a cheap but good set of roller rockers going for nowadays???

Thanks again guys.
Jonathan

 

$100 spring compressor? lol go to Sears and for $15 youll get a good spring compressor. Thats what I use and I never had any problems with it! And its Craftsman so it carries a lifetime warranty too.

 

$15???? I need to stop looking at that dumb Jegs magazine....actually they have one in there for $50, didn't see that one. But I'll take any excuse to go to Sears and look at Craftsman tools. Thanks 88 WS6.

 

before you do teh valve spring thing, try disconnecting the cat... either by pulling the y pipe or by unbolting the cat....


i seriouly doubt its the springs.

but that does sound like a clogged cat.

 

My car was falling flat on its face around 3500-4000 RPMs. Would always do this when I was at the track and would get on it. It would also do this when I was on the highway and would drop down a gear and floor it. Car wouldn't get out of its own way let alone take on a minivan..

Turned out that the bellow I was using (Brand new 91-92 TPI style) was collapsing. I would never have noticed it if I never got underneath the hood and reved the engine up while mistaking looking at the bellow itself......I couldn't believe it!! I mean this thing was collapsing as if someone was squeezing the hell out of it.

Easy fix to the problem was to insert a 3" piece of PVC into the bellow.

Now, not knowing what style of air intake you are using, I'm not saying this is your problem, but mightbe something to look at as well along with all the other suggestions.

 

I doubt it's my cat. It was doing this before I ever put a cat on it (about 6 months ago). And I put on a brand new Random Tech. bullet cat.
Anything else small like that I can check???

 

I might just try taking off the air intake assy. to rule out any restriction there.
Thanks for the ideas.

 

How do your plugs look? I would definatley check the a/f ratio at WOT before doing the springs. Ive seen many TPI cars with more miles than yours, and the stock springs are holding up just fine.

 

I will check my plugs tomorrow. I put in those terrible platinum 4's about 15,000 miles ago. I have been meaning to change them out. I will definitely take my car to a shop before I do the springs.
Thanks again...