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Old 03-18-2013, 11:43 PM   #1
gitano
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Car bucks/surges as constant throttle

My car recently began to buck (surge/stumble??) at certain speeds at constant throttle (usually half or less than half throttle) and more so when going uphill. It also seems to struggle every now and then when accelerating from a stop, it would struggle to change gears (slipping??) but eventually overcomes and gets to 3rd. I sort of ignored it because if I throttled it hard it wouldn't happen. Then I got a CEL with the following codes:

P0103 (MAF high input)
p0200 (Injector circuit malfunction)
p0300 (Random/Multiple Cylinder Misfire Detected)
p0400 (Exhaust Gas Recirculation Flow Malfunction)

This pointed me to egr system and I've read various posts on DPFE causing this, and replaced that (I have ~110k), which seemed to definitely improve things. Although it seems much better the problem still occurs at times, so I removed egr valve and used carb cleaner, and noticed that it had no gasket (!!).

After fixing that it seemed to run much smoother at idle and when cold (previously it rumbled a lot), but the bucking thing still happens.

Other threads seem to hint that the coilpack is often the culprit. Could that be a problem given the error codes? I already replaced my plugs and wires within last year or so, also the fuel filter, (fuel pump was replaced for the recall a long while back).

Does anyone think the injector circuit malfunction has anything to do with it? Thanks.


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Old 03-19-2013, 05:28 AM   #2
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If the injectors were the problem, you would experience problems at idle, and you would also have lean or rich issues. What you can do is idle the engine, press on each connector in case that connector is loose or damaged so it becomes loose. If you notice a difference in idle, then order a new pigtail connector from Ford and install.

Yeah, EGRs have to be cleaned from time to time.

Finally, check the usual suspects: PCV vacuum line. From your description, it is probably split open and sucking in air. That would upset the EGR due to loss of vacuum, and make the fuel mix too lean which would cause bucking. A new PCV might not be a bad idea either.
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Old 03-19-2013, 05:10 PM   #3
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I forgot to mention that I had replaced my PCV line with that new insulated hose from the dealer a while back (bc like you said it had collapsed). I also replaced my PCV at that time. I will check those again though just in case and also look at the injector connectors like you mentioned.
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Old 04-07-2013, 06:04 PM   #4
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UPDATE: finally got some time and checked the injector connections. Seemed ok. Then I replaced the spark plugs and now the problems are gone. The plugs seemed fine, but the gaps were a little bigger than what I remember (.058) and not all the same for each cylinder. Plus I had purchased the autolite platinum ones and wanted to get the motorcraft double platinum. These came already gapped at .052, and I seem to recall that being an ok gap size, so I just installed them as is. I have the original coilpack and aftermarket (8mm) plug wires.

Here are some pictures of one of the plugs, in case anyone thinks something is wrong. The others look pretty much the same.




These are from the fourth cylinder, and you can see a little bit of what looks to be oil at the bottom of the threads, but the boot was clean and I didn't see anything anywhere else. I think I put too much anti-seize on it last time though. The plug from cylinder 1 had the same type of "oily film" at the bottom of the threads also.
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Old 04-07-2013, 06:31 PM   #5
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Quote:
Originally Posted by gitano View Post

P0103 (MAF high input)
p0200 (Injector circuit malfunction)
p0300 (Random/Multiple Cylinder Misfire Detected)
p0400 (Exhaust Gas Recirculation Flow Malfunction)

103, This is basically saying that the MAFS is not working properly and the ECU is ignoring it.
So the first step is finding out why, all the other codes probably stem from this one.

First pull it and clean it with MAF cleaner. Reset the codes and drive for a day or so normally.
Check for codes.
If the code reappears, you may have a dead MAF (liquid water will kill one, or any liquid for that matter) as will being dirty for extended periods of time (such as running with no air filter).
Also check the integrity of the wiring pigtail. Any exposed wiring is a bad thing and should be fixed by using a new pigtail (which should be soldered, not crimped).


Get that sorted out and we'll go from there.
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