Stumble under light acceleration

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sprocket

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Well, the D.A. has a new issue now. A little background info:

This car had/has a head gasket issue but since using Blue Devil it has passed the hydrocarbon test three separate times including very recently.

I also replaced the fuel injectors but got maybe too good of a deal off eBay.:rolleyes: I suspect some of them leak. The car started very hard in the winter unless I put the pedal to the floor first to prevent fuel flow for several seconds. Then it would start right up. It starts OK in the summer but I suppose the fuel atomizes easier now.

OK now to the problem: I'm getting a stumble under light acceleration and I think it might be tied to RPM more than MPH. If I give it more gas it will take off. It never stumbles on the highway at constant speed, but if I let off the gas and coast, then when I give it throttle again it might stumble.

My list of suspects would include:
1) Dirty MAF (but I think I recently cleaned it)
2) Dirty IAC (the idle isn't the smoothest on this car either)
3) TPS dead spot
4) Something in the shifting. 2-3 accumulator?
5) The cheap injectors

Anybody have any advice on isolating the problem? I'm thinking it very well could be the 2-3 accumulator. I suppose I should try driving with the OD off?
 
Last time plugs and wires were done? And does it fall on its face type of stumble? Or hesitation stumble? Also you might be the reason why I went gen2 TPS
 
1sik32valve said:
Last time plugs and wires were done? And does it fall on its face type of stumble? Or hesitation stumble? Also you might be the reason why I went gen2 TPS
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New Autolite 764's, new Motorcraft plug wires. The stumble is kind of like there is a dead spot. More throttle clears it and I believe less throttle does too. I don't think the engine is in danger of dying. I would say it is beyond just hesitation.

I took it for a drive around town with the O/D off and didn't notice any stumble. I think I would need to drive it further to be sure that turning off the O/D eliminates the stumble.
 
Well TPS is a resistor there is a magnetic strip and a lot of times it'll wear out if it sees that position all the time. If it doesn't get a reading then it'll tell the computer to shuts down fuel but then realize that the MAFs is still indicating load so it compensates for it. Does it do it in all gears? Or just crauising.
 
With the O/D off except on the highway, I still got one stumble today on the way to work. I was coming up to a stoplight and slowed to about 20mph. The light turned and I accelerated lightly and got a pretty bad stumble. I would say the rpm was around 1000.
 
I had a similar studder when acc slow on my 95 It was trans. Merc 5 can make a difference My 97 was the same and changed to merc 5 and works as it should now
 
I think it feels like torque converter shutter to be. I barely felt any stumbling today. Maybe just very slightly. I might just change the tranny fluid. Should I drain the torque converter? What is the best way to go about changing the fluid?

Thanks for any help guys.
 
Well some of those torque converters have a drain plug this will need 2 people. There is the inspection hole with a rubber boot deal, if its not there don't be alarmed. Have someone rotate engine with breaker bar and 18mm socket either way clock wise or counter doesn't matter. It's i believe a 10mm bolt on the T.C. Let it drain for an hour or so. Enough time to pull off pan and change filter and bolt back up. If you do decide to do all this night as well jmod it. Then fill pan with about 4 quarts start for about 5 seconds shut off check level it will suck it all up. Add an other 4 and repeat process about 1 more time and make sure topped off.
 
I had my 95 and 97 both flushed and changed to Mercon 5 and it solved the stutter problem. NAPA has a little red tube of stutter fix that another member said was real good. I can't do the stuff I used to do but the right way is to pull the pan and filter.
 
On my conti I had the same issue, drove me crazy for a while. I had just cleaned my maf prior to the issue. Turned out it was a ripped seal letting air in after the maf when I put it back together. Fixed the seal, fixed the issue.
 
ground_zero298 said:
On my conti I had the same issue, drove me crazy for a while. I had just cleaned my maf prior to the issue. Turned out it was a ripped seal letting air in after the maf when I put it back together. Fixed the seal, fixed the issue.
Click to expand...

My neighbor bought back a Conti he had owned before. It idled very poorly. After some checking we discovered that there was NO AIR FILTER in it. Upon attempting to install the new filter we found out the air box was warped and the center would not clip in, so the MAF was bouncing around. We went to u-pull and got a different air box and it had a new filter too. That solved the problem.

In my case those parts should all be good, but I will check it all the way back to the throttle body. This problem is very intermittent though. On the other hand, the engine doesn't idle as smooth as it should. It's not terrible but it's not as good as my other Mark. There could be more than one thing going on.
 
ONLYTONY said:
I had my 95 and 97 both flushed and changed to Mercon 5 and it solved the stutter problem. NAPA has a little red tube of stutter fix that another member said was real good. I can't do the stuff I used to do but the right way is to pull the pan and filter.
Click to expand...

I've been milking out the transmission in my Windstar (wait, wife's Windstar or family Windstar. I don't own a mini-van) for years with that stuff. About once a year I have to add another tube. The shutter goes away immediately. Dr. Tranny's torque converter shutter eliminator. I could just try that. I was just going to go ahead and change the fluid but now I looked at it on the stick and it looks pretty good. Somebody in the recent past has changed it. Of course that is somewhat worrisome because you would think it would have solved this issue.
 
Here is an other question can't remember if you said it's been done, how about oxygen sensors? Last time replaced? If at all. They might be getting lazy.
 
1sik32valve said:
Here is an other question can't remember if you said it's been done, how about oxygen sensors? Last time replaced? If at all. They might be getting lazy.
Click to expand...

I have never replaced them. I have only had the car about 7 months. There is no CEL or stored codes. I do recall that awhile ago I was reading live data with my code reader and there was something odd...what was it? I think something didn't look quite right with the short term fuel trim on one side. That might have been before I used head gasket sealer. I'll hook up the reader again and look at the live data. I believe that last time I was thinking that an O2 sensor might be getting lazy.

Didn't I hear that the PCM is way too liberal with what it will allow from the O2 sensor readings before it sets a code?
 
I'm thinking more and more that the stumble is not transmission related. The more city driving I do, the worse it runs. The stumble gets worse but it is always at lower RPM.

I'm thinking those cheap injectors I bought might be the problem along with lazy O2 sensors. I wonder if the injectors are causing a rich condition? On the highway, the PCM is able to adjust based on the O2 sensor readings, so it runs fine, but around town at lower RPM with constant change in speed, the PCM just can't correct fast enough.

Does that make sense?
 
sprocket said:
I've been milking out the transmission in my Windstar (wait, wife's Windstar or family Windstar. I don't own a mini-van) for years with that stuff. About once a year I have to add another tube. The shutter goes away immediately. Dr. Tranny's torque converter shutter eliminator. I could just try that. I was just going to go ahead and change the fluid but now I looked at it on the stick and it looks pretty good. Somebody in the recent past has changed it. Of course that is somewhat worrisome because you would think it would have solved this issue.
Click to expand...

I have a Mark VIII. Had a TC shudder that started at about 67k. Flushed and changed to Mercon V. Within 200 miles it was greatly reduced. Added Dr. Tranny, and within 20 miles, it was gone.


(knock on wood)
 
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