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Engine Missfire When Warm.

P

Pepse

New CEG'er
Joined
Jul 30, 2005
Messages
18
Location
Wisconsin, USA
This has been going on for about 6 weeks. When car is cold it runs great. Afetr about 5 miles of driving (when fully warmed up) it has a very noticeable miss when going up hills or even when I add some gas. It occurs at any speed. When cruising down the freeway or a highway there is no miss unless I increase speed even a little. I found my code reader yesterday and did a code check and the results are: (key on-engine off) 332-Insufficient EGR flow detected, 335-EGR sensor circuit voltage higher or lower than expected during KOEO, 336-EGR sensor circuit voltage higher than expected / exhaust pressure high. Key On Engine Running, 336 (same as above), 538-Insufficient RPM change during KOER Dynamic Response Test. As for the codes 332, 335 & 336 I have had them codes come up for 2 years and did not have this missing problem 'til recently. And NO the CEL rarely if ever comes on. Plugs and plug wires have about 14K, fuel filter was changed about 18K ago.

Later. Pepse.
 
Pepse said:
This has been going on for about 6 weeks. When car is cold it runs great. Afetr about 5 miles of driving (when fully warmed up) it has a very noticeable miss when going up hills or even when I add some gas. It occurs at any speed. When cruising down the freeway or a highway there is no miss unless I increase speed even a little. I found my code reader yesterday and did a code check and the results are: (key on-engine off) 332-Insufficient EGR flow detected, 335-EGR sensor circuit voltage higher or lower than expected during KOEO, 336-EGR sensor circuit voltage higher than expected / exhaust pressure high. Key On Engine Running, 336 (same as above), 538-Insufficient RPM change during KOER Dynamic Response Test. As for the codes 332, 335 & 336 I have had them codes come up for 2 years and did not have this missing problem 'til recently. And NO the CEL rarely if ever comes on. Plugs and plug wires have about 14K, fuel filter was changed about 18K ago.

Later. Pepse.
Click to expand...
So were you just giving us something to read or did you have a question? I think from what you posted you have some places to start looking and cleaning.
Karl
 
So, elaborate. I try to give all necessary info when posting about anything. As far as I can tell I don't have any air leaks. So, clean what??

Pepse.
 
Pepse said:
So, elaborate. I try to give all necessary info when posting about anything. As far as I can tell I don't have any air leaks. So, clean what??

Pepse.
Click to expand...

This kind of stuff can be elusive, but the things that came to my mind first were: a dirty MAF, a bad throttle position sensor, or a fouled catalytic converter, though I'd expect that last one to kick a light. Since its only under warm throttle, I'd check the TPS. Clean the MAF while you're at it, and see where that takes you. :cool:

Have you been through the plugs / wires in the past few weeks? Any oil in the wells?
 
MAF? Didn't think of that, haven't cleaned it in about 14 months. TPS? Thought of it, but thought I would get a read on the coder. Plugs/wires? As I mentioned not really that old, but begrudgingly, I will look into it; those da@* plugs on the firewall side are a pain. Also, stupidly, I would like to imagine that the plugs/wires would be of same quality as what I grew up with (yeah right), and that they would be okay.

As for the TPS, how would I determine if it is bad??

Pepse.
 
My misfires were the result of a spark plug wire not completely set right (cylinder 4). They had about 2k miles on them. I pulled all the wires completely off, put dielectric grease on the contact points, and reseated everything until it clicked into place.
 
Yeah, 2 months later and the old man responds :-|). Anyway I cleaned the MAF, made sure all the plug wires were on tightly (both ends), checked for air leaks, FOUND ONE; the crankcase ventilation tube had a deteriorated elbow on the valve cover. Replaced it, no change. Well ever since I changed plugs and plug wires at 98,xxx miles it has acted kinda crappy (currently 126K). So, I have been blaming the cheap Advanced Auto branded wires or possibly the Autolite Platinum plugs. So, I bought a set of Motorcraft platinums and put them in today. Problem solved. It actually seems a little more responsive than when I first got the car. I don't seem to have that air starvation feeling when slammin' the gas from a dead stop. Time will tell on that one. So, I was a little surprised that it was the plugs and not the cheap A/A plug wires. But then I have in recent years determined that OEM, altho spendy, is actually the better way to go. The cars I grew up with in the '60's thru the mid '80's would work good on non-OEM parts. But with the over-computerization of the newer vehicles OEM seems to be better.

So, only 28K on the plugs, doesn't sound good to me. But then maybe this newer stuff ain't made to last as long as "from the factory parts".

Also, as for the plugs I removed? Nothing unusual. They seem to match the "normal" plug picture in various books.

Overall tho I think the next few days will give me a better idea if the problem is truly corrected. Today might have been deceiving; 37 deg F, humid, foggy. January thaw up here in the Norseland :-).

Later. Pepse.
 
Pepse,
you should be using Double Platinums for these motors.

Have you checked the fuel pressure? When was the fuel filter last replaced?


More often than not, a miss or stuttering while driving is a symptom of either spark or fuel delivery.
 
As for double plats I seemed to have cured the problem with Motorcraft OEM plugs. Fuel filter? About 15k ago. Altho I plan to replace that soon, because I don't recall how often they should be replaced.

The one thing that didn't change is the fact that the car has to idle for about 2 minutes after sitting for an hour or more. Still acts like it is starving for air, unless I slam the throttle in which case it is getting lots of air.

Later.
 
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