Engine missing issue

[Wayfarerwalk]

I have a 98 EB 5.4 with less than a month old tune, injector and TB clean. It was doing this chugging/missing when I have it tuned. They (local dealer) claimed there were no codes and when I picked it up it did run good for about a week. At the same time, under normal acceleration I was getting pinging from the valves. Ran some premium gas through it for 3 tanks and the missing and pinging stopped along with a mild increase in mileage, plus the acceleration was fantastic. But when I would get to the 1/4 tank mark, the missing would start again. I just put regular back in it and its a missing dog again. Being mechanically challenged I was wondering your thoughts. I was thinking fuel filter (about 6 months old) or fuel pump, but with it running so good on the good stuff, it kinda stumps me. Thanks for any help.

 

[Jeff532003]

Considering your experience with premium gas it's leads me to think your timing maybe way to far advanced causing the ping and miss but this doesn't explain the quarter tank issue. If it timing then it's either a bad sensor sending incorrect info to the ECM which should throw a code or a bad ECM itself which could explain no code and the issue. It also could be a mechanical problem with the timing chain or tensioner. Without hearing and experiencing the issue it's really hard to pinpoint so all I can do is guess. If its pinging really bad I'd think it might also trip the knock sensor and if its missing you should have a missfire code as well which again makes me wonder if your ECM hasn't gone bad.
When they did the tune up did they run a top engine clean through it? Sometimes extreme carbon build up can cause hot spots in the cylinder causing early detonation. You might also try changing the EGR valve and cleaning out the ports on the throttle body spacer. There's a good how to on here that I'll find and link for you. If you do that clean the IAC valve while your at it. It's easy and you'll be right there but I don't think that's causing your issue. Just good preventative maintainance.
If none of this works you might do better finding a reliable local shop. Dealers can be hit of miss. All depends what tech your car winds up going too. Some are great and do a through job, some only care about hours. A small independent shop, that guys likely to be more through to get your repeat business. Good luck.

 

[FordandPolaris]

Carbon build-up can also cause the combustion chamber to shrink, causing premature detonation. Running premium fuel would help to combat that. Try changing brands of gas too. Might want to look at doing a sea foaming of the gas and if it still isn't fixed maybe a top-end cleaning/rebuild.

 

[ArtGamer60]

Good advice from the previous posters , these days and all the computer controls and sensors , you need to invest in a code reader , otherwise it is like trying to find a needle in a haystack . I was having problems when mine was real low on gas , it was missing and chugging , the engine light came on , turned out to be sediment in the tank , but yours starts at 1/4 , it has to be something else .

 

[Wayfarerwalk]

Thanks guys for the info. I think I should first invest in a good code reader and see if it throws a code when it is missing, then I'll attempt the top end cleaning. As for the timing, I would have thought they would have checked that when they tune it, but it is something that will have to be checked. One more thing that just remembered is that when idling, I hear a squeaking for the front of the engine while in gear, it quits when its put in park. I was thinking the idler pulley. Thanks again for the info.

 

[Jeff532003]

Thanks guys for the info. I think I should first invest in a good code reader and see if it throws a code when it is missing, then I'll attempt the top end cleaning. As for the timing, I would have thought they would have checked that when they tune it, but it is something that will have to be checked. One more thing that just remembered is that when idling, I hear a squeaking for the front of the engine while in gear, it quits when its put in park. I was thinking the idler pulley. Thanks again for the info.

I recommend you pick up a stethoscope with a metal rod on the end for diagnosis purposes.
If you have a harbor freight close by they're really cheap but autozone or the like probably sells them too for not to bad. This way you can put the rod near the different pulleys and pinpoint where the noise is coming from. 5.4 is also known to have timing chain tensioners fail and you'll hear that squeezing as the chain runs over and eats the guides.
Good luck