slowintegra92

I have a 94 Toyota Land cruiser with the 4.5 liter inline 6. It has a shit ton of miles but runs good..a solid truck. Well the only problem that has showed up since i have owed it over a year is it start to sputter or miss right around 1900 rpm's. well i figured it looked like the plug wires and such were old so this weekend it needed a oil change so i figured i would tune it up a well..so i changed the oil, fixed a dry routed hole in the intake hose, cleaned the MAF with proper MAF cleaner, changed the plugs(NGK's) of course,wires, dist cap and rotor...Now the issue is as follows...it now misses at idle but does idle..that is new and when driving it misses up until 1900 rpm. After 1900 it cleans up and is super smooth and has actually more power(feels) then before...so its like the same problem as before is still there but the tune up actually made it more evident..but the entire rest of the RPM band is way smoother and powerful? So i need some help with where to go on this..again i have drove it with the slight miss for over 6 months daily and even pulled heavy boats and all..never a big issue..

toyota_aristo

Any smoke? Did you have to gap the plugs at all?

f-av8

I would check the gap of the plugs and do you drive it often.?

slowintegra92

the plugs gap are correct and i drove it daily for over a year..no it does not smoke of any kind...the head gasket is not blown. The oil and coolant are clean. And it would not run perfect at any RPM above 1900 if that was the case..i need something else that a tuneup would make this problem worse..and no i never messed with the timing. Fab..get in here..please

slowintegra92

and yes i checked the firing order..it is indeed correct. Do you think and EGR valve that bad could cause this? Kind of and expensive shot in the dark 170 bux...i am going to check the timing says it should be 3 degree's.

slowintegra92

Need some help Fabrik8..

ProbeGT-ZE

Do you have a CEL? I doubt it's the timing. Sounds like it's either a vac leak, tps, or maf problem.

Fabrik8

First and foremost, reset the ECU. Any learned long- and short-term fuel trims, etc., should be reset after your tune up as a baseline.

Yeah, it could be a timing problem, but that would usually affect power and smooth running over most of the RPM range. The ECU can only change timing over a certain range, so if the static timing is off than the ECU usually isn't able to compensate over most of the RPM range. That being said, if you're running into the wall on timing before the tune up, you should be running into the same wall afterward.

The plugs, cap, rotor, etc., shouldn't change anything really. But, the dry rotted hose and the dirty MAF sensor might have covered up a problem somewhere else, like you said. I don't think it's an EGR problem, because that generally won't give strange misfire-like symptom. It's much more likely that it's something like a MAF or TPS problem, and cleaning the MAF sensor has probably affected where/how the ECU is operating within the fuel and ignition maps and correction vectors. This just really sticks out as being a classic MAF problem, but it's a hard one to actually diagnose without replacing things because it's hard to know what the MAF should actually be reading at any given load/RPM operating point. If you have an factory service manual, it should have voltage values for the MAF at idle, etc., so that's a starting point. At least it's misbehaving at idle, because that's much easier to troubleshoot than most other operating points. So check that the TPS is calibrated correctly at idle, and see what the MAF is reading and compare that to the service manual values.

I have to confess that I know absolutely nothing about that particular car, so I can only offer generic directions to go in for troubleshooting. I never touch SUVs or trucks if I can possibly help it; I've never been interested in them and they're not as fun or easy to work on as cars usually.

slowintegra92

Thanks for all the help and a direction to go..do you think that replacing the coil should be in the list of things to do as well? And when you say reset the ECU u are saying just unhook the battery for like 5 min? Thanks

Fabrik8

Usually you can pull the ECU fuse and wait, or disconnect the battery and press the brake pedal.

I don't think the coil would be part of the problem, coils usually have misfire problems all over the RPM range when they're misbehaving. You're having problems below 1900RPM, which generally points at a sensor problem.