Contour Enthusiasts Group Archives Forums General Troubleshooting Stumbling under load - worse when cold

Just now trying to diagnose a new stumbling/studder problem.

This is on a 2.5L MTX.

When the engine is started cold, anything more than gentle acceleration causes serious engine bogging. This was certainly not always the case. Normally, even in artic temps, once the engine was started, it accelerated perfectly.

The problem goes away for the most part after warmed...but not entirely.

Idle is perfectly smooth. When engine is at least partially warm, I can feel a subtle stumbling occur under light to moderate acceleration. Once the secondaries kick in, it revs nicely and I can't seem to detect the stumbling any longer.

I've replaced the plugs (+4's) already - using Magnacore wires, cleaned the TB and EGR passages. EGR holds vacuum but haven't tried the vacuum to EGR to test the idle yet.
DPFE is the original one (silver).

The stumbling isn't bad, but it's noticeable and it's annoying.

With nothing more than this to add to your post, I hope you don't take it the wrong way.


How old are your plugs, and WHY ARE YOU USING +4's????


I'm not the least bit upset, or anything, I just didn't know if you hadn't read about how badly they perform in this system, or if you didn't particularly care.

Seriously, though:
Welcome to CEG.
Read through our "archives" and also through our current posts. Learn to use the search feature, and read all the faq's and how-tos. I applaud you for a VERY WELL writte first post, and encourage all others to strive to make their contributions to CEG in such a manner.

I would consider changing to Autolite APP764 Double Platinum plugs (2.99 at Autozone), gapping to 0.054 (pre-gapped is balogna!!!). EGR vacuum test is simple enough to perform, as well, though *should* provide little to no insight in this problem..

The Ford Factory CD references the CKP(crankshaft Position) and CMP (Camshaft Position) sensors when stumbling or bucking on acceleration, as well..)


Ray

try this first,
check to make shure your fuel pressure regulator is working if it is then get a new ford coolant temp sensor that should fix the cold hesitation , if it still bogs after that ditch the +4's for some autolite double plats and if it still bogs after that get some new wires.

Ray,

I orginally put the +4's in about 50Kmi. ago when they first came out and they've worked beautifully since. This current problem is pretty much an overnight change in the way the engine is running. If I hadn't just spent almost $40 on the plugs and an hour installing them, I'd change them for the Autolights.

....btw, I certainly did go through the archives. As expected, I did see many posts of people using the +4's with good results...and also those that didn't like them. I seem to fall into the former camp.

I'll check my factory tech manual for the CPK and CMP tests. Thanks.

As for the coolant temp sensor....that's definately an interesting one since I've been seeing some weird variances on the coolant temp guage over the last couple months. In the past years, it's stayed rock solid midway. Then lately, it started going higher. Now, it sits just before the N in NORMAL for nearly 90% of the time.

the coolant temp sensor tells the computer the temp.

the coolant temperature sending unit tells the guage the temp.

sounds like you need a new themostat to get your coolant temp up to normal but that wont fix your boging problem

Hey moderator, you need to change your bio to "married with children."

Ja....wasn't reading through the archives and just discovered this.

Am I correct in thinking that even IF the PCM thought the engine was colder than it really was, it would continue to enrich the fuel delivery (to some degree) which wouldn't cause the bogging that I'm seeing?

The one thing that I keep thinking about is how the problem seems to go away once I get the secondaries opened under high-reving acceleration. What changes at this point? This might lead to clues.

Ok...thnx.

Is the coolant temp sensor the one right below the TB and EGR?

yes it has 2 wires coming out of it