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Discussion Starter #1
(91000 original miles no bull) I am waiting on a scanner to see if it will help me. Not getting any codes. The beast runs fine until it approaches running temperature then starts to deteriorate until a stall occurs. Over winter it ran fine unless I took a long trip but the cooler weather helped reduce the symptoms. It doesn't get hot according to the idiot gauge. I was told to replace the cooling temperature sensor attached to the thermostat housing because it some how affected computer adjustments. That didn't work. I checked all ignition wiring and related parts and all check fine. I do notice it starts to run a little lean and the fumes seem heavy. The engine will seem like it's missing cylinders and back fire a bit. There is no smoking related to this problem. MAF replaced and ran sea foam through the system. Removed and replaced Plenum for valve cover gaskets and it looked like the seafoam did a good job. (FYI) I highly recommend ithe sea foam when your power plant gets to running sluggish. I was thinkin CAT converter but I don't know how to check it. This problem started last summer and it ran okay during winter but I have to get to the bottom of this. I have an F150 Supercrew as a primary vehicle so I have patients to spare. I'm a Ford man all the way.
 

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A 91 5.8 doesn't use mass air, it's speed density. So I dunno what you replaced, but it probably wasn't the MAF.

Which temperature sender did you replace? There are two of them, the single wire sensor in the lower intake manifold is the ECT, is that the one you replaced, or did you replace the temperature gauge sender?

When it stalls, does it start up after that (regardless of condition), or does it just crank?

Search for pulling codes, you don't need a scanner, and your CEL doesn't have to be on for you to have codes.
 

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Discussion Starter #3
Hey thanks for a reply. I replaced the two wire cooling sensor on the thermostat housing. As far as the other ssensor goes that probably was the TPS we were exchanging. Sorry I must have mixed it up with my 2001 F150. We switched it out with one he said was known good but there was no change so we reinstalled the old one and adjusted it by the manual. When the engine reaches running temp it starts to stumble and it seems like it's getting too much gas. When it stalls you have to let it cool down a little before it will start again. It doesn't get very hot or overheat but the fumes are heavy and it boggs down and backfires a bit. It doesn't flash any codes but I got a ProLink 9000 scanner from a friend and I'm going to hook it up and see what I get. Thanks again for your help. I'm doing my best to explain what I've done so far so thanks for bearing with me.
 

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Okay, the two wire sensor, isn't your ECT. That's your gauge sender.

Don't bother with the scanner, a paperclip will do the exact same thing as the scanner. Search for "how to pull codes" from the user Steve83, and check out www.fordfuelinjection.com.
 

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Discussion Starter #5
Checked out your link; Good info. I looked at ECT pic and that is what I replaced and it had no change. If I had the link before I could have saved 18 bucks. I will pull codes as you suggest to narrow it down. I will also check the wiring back from ECT. This is some good info, I appreciate the input. This has been a thorn in my side for quite a while and I need to get it fixed. I have a friend with a Pickup with the same motor same year and he's having the same problem. It sounds like it could be pretty common with this year and motor. Anyway thanks again and I'll post what I find out after the weekend. I'm way ahead of where I was. Thanks
 

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you might try popping a hole in the exhaust upstream of the cat converter sounds like it might be your problem considering you cnat get it to start hot, if it continues to run youll know if not run a self tapping screw into the hole to plug it : )
 

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Discussion Starter #7
Out of desperation I checked my EVP sensor and it didn't read correctly. I installed a new one that tested good and the truck ran better than it has before the sensor. I ran tests with the scanner a friend let me use and I got some codes. I got a 22,41 and a 33 code. One of those is a no EGR open detected. Another was MAP or BP sensor. What is a BP. Do you think the EGR valve is not opening? I didn't get that code until I replaced th EVP sensor which I know was bad because the resistance readings were way off with vacuum and no vacuum. The truck ran and did not stall but it ran like crap in the normal heat range. it has ran that long. This is getting on my nerves. Do you think I should still poke a hole in the CAT? Thanks for all the help on this. My friends truck is doing the same thing.
 

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The MAP is your manifold absolute pressure sensor. If you got a code for it, chances are it's probably bad.

It's located on your firewall, and has a vacuum line running to it.

I don't think the problem is a plugged cat.
 

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Yeah the MAP sensor (BP sensor on a MAF vehicle) will cause problems and can be temperature sensitive, i.e. if its going bad then the truck will act up with temp. changes. It is closer to the passenger side on the back firewall. It has a vacuum line plugged into it that goes to your manifold. Check that line its hard plastic and rubber and has been known to deteriorate over time. The sensor has 3 wires coming out of it. You can get a replacement from the dealer or any auto parts store but I will tell you from experience DON'T purchase that part from Auto Zone or Advanced! Go to NAPA or O'Rilleys. I've gotten that part bad out of the box from Auto Zone and from Advanced.
Is your check engine light staying on all the time? Does it turn on when its acting up? Where were the codes thrown? First set is active codes and second set (after the pause) is in the KAM (keep alive memory)
 

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Discussion Starter #10 (Edited)
I'll test the MAP if possible. What about the EGR not opening code. EVP is working now and I got that code. Should I repair or replace MAP and see if I get the EGR code again. Do they clog and can it cause my problem? Is there a test for the EGR itself or a relay I should look at. The PL9000 starts receiving codes as soon as I initiate the engine run test and the engine runs fine. As the temp goes up engine begins to run rough and light starts flashing. Lgiht does not remain on if I turn off the engine and it now start right up but runs rough. Engine no longer stalls so I think I may have this problem licked soon. Thanks again for the help! I'm learning a lot working through this problem.
 

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Discussion Starter #12
I replace MAP with known good one cleared memory. Ran it a long time until it started to run rough. Ran test and got same code 33. Pulled EGR and tested with vacuum pump and it holds. vacuum. What else can I test in the EGR system. This problem is kicking my ars.
 

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A vacuum leak in the hard plastic lines could be your problem. I read through your posts and didn't see any mention of the vacuum lines. You might want to check them out, as they tend to crack and break rather easily.
 

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When was the last time the spark plug wires were replaced? A symptom of it acting up as it gets warmer is a good sign of your wires being bad. I've seen it ALOT!
 
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