Yesterday trouble has begun. My Expy is 98 4WD, 4.6, 91 000 miles. I went with warn engine when i just felt little hesitation in initial accelaration. After a few miles check engine ligts start to flash and then went on. I stopped and trying to find out what happened. Nothing. I disconnect battery to reset memory and went on. But when I stopped for example at traffic lights idle went down to 400 rpm and in a second went back to about 650 RPM. I went a few miles to shop center and after half our Iwent back home. Idle when stopped was fine but i felt little shaking every 5-7 sec when stopped and in initial accelaration I still felt little hesitation and after a few miles check engine started to flash again and then went on. In the evening i tried to start cold engine, idle run fine but engine run very hard , irregularly like some cylinder did not work.
Spark plugs and air filter was changed a few weeks ago. A month ago I cleaned MAF but only with one spiral I was succesfull, the second one stayed black. Is there any way how to check myself that MAF works good? Only what I know that manifold exhaust gasket is leaking and will be changed this week (it will be horrible work as I was said by mechanic). Can be all caused by that? Any other ideas where the trouble should be? Thanks for your help as I live in Europe in Czech Republic and it is little bit more diffucult to find good service for my Expy. As well part are two times more expensive than in USA (I was said due to transort, VAT, coll and dealer margin) For Example 8 Motorcraft spark plugs cost me 100$

 

Archibald I read your situation and I have great news!!!!!!! I just saved bunch of money on my car insurance by switching
to gieco.

 

that was WRONG! funny but wrong..... hahahaha help the man out, he's not even in the US for Pete's sake....

 

Archibald,

Is there any place near Prague where you can get an OBD-II scanner hooked up to read your stored codes? If the check engine light is on, then you'll have a diagnostic code stored in the PCM to help you troubleshoot. Once you know the codes, lots of folks on this site can help you.

 

Gibsonj, (you know Prague?)yes there is only one service in Prague which have OBD scanner for USA FORD. But the first I would like to know ideas from folks here before paying 50$ for diagnostic. I guess it should be IAC. I tried to clean it yesterday it was really dirty - black and I was not able to clean it perfectly it stayed black. After installing back cold start was much more better engine run almost smoothly, but when running and stop idle went again down to 500 RPM and then back to 650 RPM. As well sometimes idle was fluctuating between 650 and 800 RPM. But check engine lights is off now. I will buy new IAC and let you know. But at my mileage maybe o2 sensors are bad too.

 

Archibald,

If your O2 sensors are failing, it will definitely set a hard code and cause the MIL to illuminate and stay on.

 

Gibsonsj,

today I ordered new IAC, front O2 sensors and PCV valve. I hope my trouble will be solved.

 

Yesterday new IAC and new exhaust manifold gaskets were replaced. Cold start was great and smooth, idle was fine. But one problem still exists. I can feel some irregular something like light misfire when in gear in idle (in P or N there was no misfire). I was listening to engine, and at the time of this misfire I heard some vacuum noise like somewhere something puffed or took up. As well when engine is switched off I can hear buzzing from EGR valve sensor, is that normal or it should be replaced? Please can somebody send picture where PCV valve is located (98, 4.6 engine)? I really cannot find it.

 

Is your check engine light still on? The IAC valve normally won't trip the light. At 91K miles, your problem(s) could be many different things. '98 4.6L has plug wires so it could be them, could be a vacuum leak in the hose to your pcv (on my 5.4L it's located on the passenger valve cover toward the back of the engine), could be EGR, what about fuel filter, etc.... IF you have a stored code, get it read as it could be a lot cheaper to fix one thing rather than continuing to take shots in the dark.

 

Light is off now. I guess light went on due to manifold exhaust leaking - bad info from O2 sensors. Anyway I will change them next week. On Monday I will go to Ford service to diagnostic engine but at this time no code is stored (After changing IAC I reset PCM) and I will ask them to change fuel filter as my mechanic does not have the tool. Now I can say that after changing manifold exhaust gasket and IAC the car is running much better than 2 years ago I bougt it only when it si cold I can feel some little shaking or hesitation which desapper in a few seconds. I have new PCV valve with elbow at home but I cannot find neither PCV valve and PCV hose.