Engine/Transmission (1998.5 - 2002) Lope/miss with light throttle? anyone

[rivercat]

I just put in don m's mach 4s and now i have a lope when coasting or cruising with very light throttle bettween 1500 and 2100. I have spoken with another member that gets the lope with or without the m4s. What would this be. ALL THE SIMPLE THINGS HAVE BEEN CHECKED. This is a deep problem.

 

[Will Manchester]

I have a lope / shudder under very light throttle as well for almost a year now.

When my truck is cold, there is no lope at all - sounds totally normal. As the truck warms up, it gradually gets worse and worse. On a hot day when working the truck or doing a couple of WOT runs, it gets very noticeable & annoying. It must be off of idle and probably less than 1/8" throttle to get the lope / shudder. Idle (zero throttle) sounds totally normal.

There are no codes. The tac is solid as a rock when its loping.



To date, I have:

1. Replaced VP44

2. Multiple sets of injectors, including trying a known good set of stock injectors (Don's M4's have been the smoothes so far!)

3. ECM

4. Adjusted valves

5. Installed a FASS 150

6. MAP sensor

7. IAT sensor

8. APPS sensor (calibrated it on install, added a redundant ground as well)

9. Cleaned all my grounds

10. Removed alternator from charging circuit (suspected noise)

11. Removed TST box

12. ??? maybe more, but this is all I can remember



So far, I can't say I've fixed a thing!

 

[tmacc]

Yup. I got it after installing some 1. 6s. Mainly in warm weater. Runs kind of rough at start up in the morning. I'm just ignoring it for now. It did not do this w/ some BD1s that the 1. 6 replaced.

 

[R-N-R]

Mine used to lope like a dragster when I had DD3s in it, the M4. 5s smoothed it out a bit.

 

[Will Manchester]

About a month ago I threw in a set of known good stock injectors (running out of ideas). My problem injectors got worse after installing the stockers.



I guess one more thing to note: For about a year now, my truck has been difficult to start in cold weather, probably 30 degrees and below. Only happens first thing in the morning. When it tries to start, it runs at about 200 RPM and throws tons of nasty light grey smoke out the pipe until I shut it off. Usually takes about 2-4 tries to get it to fire. I was thinking that my fuel supply line was leaking allowing the air to enter the injectors lines overnight, but I injectors a FASS pump this summer including a 1/2" stand pipe - so the ENTIRE supply side is brand new. And sure enough, once is started getting cold again, truck didn't like to start.

 

[rivercat]

make sure your crossover tubes are in good shape and seal good especially on the injector end. with an internal leak you would lose prime overnight. Hohn, care to chime in?