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91 XR7 5.0L skipping

Hello all, been lurking for a while but now I need some help.

I have a 91 Cougar XR7 with the stock 5.0L HO. When under moderate to hard acceleration, the car seems to skip a beat and miss. I can attempt to replicate this by running at the same rpms in 1st gear but skipping does not occur. Because of this I'm thinking that this is more a tranny issue than an engine or fuel delivery problem. The engine has been well maintained and I gave a compete tune-up in the summer thinking that would resolve it. Idle is perfect and doesn't skip at low to low-moderate acceleration, aka normal driving. The cat is not my primary mode of transportaion so I can spend the time to diagnose and fix it. But now I need to know what else to look at.

Any ideas? thanks in advance

Reply to
John
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but skipping does not

Keep in mind that due to the lower gear ratio the motor won't be under near as much load at a steady rpms compaired to running in drive or overdrive.

You said that you gave it a normal tune up. Please go into more depth as to what you did. some people's normal tune up can be way different than others. Have you checked the EGR valve?

MadDAWG

Reply to
MadDAWG

Tune up: cap. rotor, wires, plugs, pcv valve, fuel filter, fuel injector cleaner in the tank, air filter, oil & fileter change (needed it anyway). Even disconnected the battery to reset the ECM. Engine has 150K on it, burns no oil, old plugs looked good enough to use again but opted for the replacement anyway.

I understand what you're saying about not being under load like in

3rd/overdrive. Also, the location of fuel in the tank will be different as well but I think I'm reaching on that one. No I have not checked the EGR valve. Is that basically removing it and cleaning the passages? I assume it should be closed at WOT but gradually open as engine speed and vacuum increase from idle.
Reply to
John

Just out of sheer curiosity, did you check the timing on the car again?

It *shouldn't* change but it never hurts to check. The grade or quality of gasoline you've been getting could affect that as well... but that's a bit of a reach. The gas tank position doesn't matter... the tank has a low spot right by the fuel pump pick-up to ensure gas is at the pickup under most conditions even on an almost empty tank.

Sounds most likely spark related, then perhaps fuel related. You're getting no codes or MIL?

JS

Reply to
JS

No codes, no CEL, what is MIL? Timing did not change and is set at 10 degrees BTDC IIRC.

Reply to
John

Malfunction Indicator Light (MIL) = Check Engine Light (CEL) :)

Reply to
Garth Almgren

You should be able to just plug the vacuum line and drive it for awhile. If it goes away then its time to replace if not put the line back on.

MadDAWG

Reply to
MadDAWG

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