1991 Civic - Loss of power at specific RPMs

[Brian Heun]

Hello All,

My wife is running this season with a 1991 Civic in ITC. We are borrowing the car for the year and part of the deal is that we will do some work on the car's needs.

One issue has been dogging the car since the engine was rebuilt two seasons ago. From about 4800 rpms to about 5200 rpms it seems to hit a dead spot in power and it sounds like it is mis-firing.

My thought is distributor. However, before I tear that out I wanted to see if anyone has experienced a similar problem and if so, any input on the cause and/or how to correct it would terrific.

Best regards and thanks in advance,

Brian Heun

1991 Honda Civic
ITC #27
(on generous loan from Meg Meyer)

[joeg]

I know the car well. Didn't realize it had a problemo since it always ran strong.

You might want to try some obvious things, like plugs and wires first.

[Ed Funk]

Check with Jinx Jordan, seems like he had a similar problem with his.

Hope you don't get it fixed! That car was too strong for our carb'd ITC Hondas!

[spnkzss]

I had problems before I switched to A, and have another friend with problems with his B Civic.

Where did you pick up your tach lead? Don't do it out at the distributor.

Jinx changed his engine harness out and that solved it for him. Try to find an unmolested engine harness and don't splice anything. See if that takes care of it.

Just remember the '88/'89 engine harness is different from teh 90/91. If you find an '88/'89 you need to change out the body harness too.

[Brian Heun]

Thanks for the input. I will confirm with Meg but I think the plugs and wires were changed after the problem was first observed and it didn't solve it.

Thanks again.

Brian

[spnkzss]

Thanks for the input. I will confirm with Meg but I think the plugs and wires were changed after the problem was first observed and it didn't solve it.

Thanks again.

Brian

FYI, I don't mean spark plug wires. I mean engine wiring harness that wraps completely around the motor for all the sensors that plugs in at both sides of the firewall.

Something in the main harness seems to cause the issue. I never did find mine, but I have to think it was caused by something in the tach/distributor lead.

[Brian Heun]

Thanks for the clarification. Actually, I did confirm that the plugs and wires have been changed since the problem started to no avail.

Will check the wiring harness, particularly the tach lead.

Thanks again for all the input.

Brian

[blackGreenRex]

Brian
Is this car the dual point throttle body injected model?
I had a similar problem with my 1990 ITA CRX DX model after I removed the metal plate found inside the air intake chamber (Looks like a little restrictor plate bolted in front of the opening to the chamber).
When removed the car would sputter and mis-fire at around the same RPM range. When I reinstalled it the car ran fine again! Did the engine builder maybe forget to put that back in?

Konrad K.
1990 Honda CRX DX-ITA
Chicago Region SCCA

[pavis]

Agree that distributor could be the problem. We had a similar problem. One plug was fouled and replacing it "sort of" fixed the problem. Eventally replaced the engine harness at the end of last year and the issue is gone.

Pete
90 CRXsi ITA

[Brian Heun]

Thanks for the input everyone, really appreciate it.

With regard to the wiring harness, it appears original. Therefore, any concern about prior modification doesn't seem to be an issue. However, if is possible that the old harness may simply be developing a problem?

As for the throttle body, I will need to check. I don't know the car well enough yet to answer the question.

Again, thanks. I have a number of things to check but at least I can go one at a time until the issue is traced.

Thanks again for the help.

Brian

[joeg]

Brian--Rest assured, no one fooled with the throttle body at the last engine rebuild.

[spnkzss]

Brian
Is this car the dual point throttle body injected model?
I had a similar problem with my 1990 ITA CRX DX model after I removed the metal plate found inside the air intake chamber (Looks like a little restrictor plate bolted in front of the opening to the chamber).
When removed the car would sputter and mis-fire at around the same RPM range. When I reinstalled it the car ran fine again! Did the engine builder maybe forget to put that back in?

Konrad K.
1990 Honda CRX DX-ITA
Chicago Region SCCA

Are you talking about the 90deg piece of metal that stands up straight in the stock air box right before the opening to the throttle body?

[blackGreenRex]

Are you talking about the 90deg piece of metal that stands up straight in the stock air box right before the opening to the throttle body?

Yes I believe we're reffering to the same piece. It sits straight up inside the air chamber assembly after the opening from the air box tube. it looks very insignificant but it made a difference in the way the car ran at higher RPM when removed.

Just trying to brainstorm some other possible solutions, but it could very well be the harness or distributor.


Konrad K.
1990 Honda CRX DX-ITA
Chicago Region SCCA

[spnkzss]

Yes I believe we're reffering to the same piece. It sits straight up inside the air chamber assembly after the opening from the air box tube. it looks very insignificant but it made a difference in the way the car ran at higher RPM when removed.

Just trying to brainstorm some other possible solutions, but it could very well be the harness or distributor.


Konrad K.
1990 Honda CRX DX-ITA
Chicago Region SCCA

No no, just an interesting observation. I also found it to kind of go away by opening the air lid. Not completely, but it helped. Again, just interesting. I spent a couple years trying to figure that one out before I built a new car.