rough idle

[deadbeat son]

I searched and read related threads before posting, but my issues seem a little different.

Last night, I picked up my 94 SWB after having some service work done. I had the valve cover gaskets and fuel filter replaced, and I had the oil pan dropped, cleaned, and reinstalled. I picked it up after hours, so no one was available to answer my questions.

My truck seems to be idling rougher than it was when I dropped it off. From outside the vehicle (and with the hood open) the engine appears to be running smoothly; everything sounds fine. When sitting in the driver's seat, it feels like it's running really rough and possibly missing. This happens whether or not the tranmission is in gear, and continues even if I use the accellerator to speed up the engine while in neutral or park.

I doublechecked the plug wires, and they're connected well. Also, if I hold my hand to the exhaust and smell it afterward, there's no raw fuel smell.

Plugs and wires were replaced within the last 3000 miles.

The following items have been replaced within the last 1000 miles:
IAC (Chevy Astro replacement)
Coil (Lucas)
Dist cap and rotor (Lucas)
Ignition module (Lucas)
EFI and fuel pump relays (Bosch)
Exhaust (custom, stock style)

Also, the timing was set.

Within the last 250 miles, I replaced the fuel pump with a new Delphi assembly (not just replacement pump motor.)

Before the service work, the engine didn't feel this rough at all. I had the VC and pan work done just because I was annoyed with oil puddles in my driveway, and the fuel filter was replaced just as preventive maintenance. I believe the mechanic disassembled the FI plenum to change out the VC gaskets. Could this be the root of the issue?

This weekend I plan to clean the MAF and check for any vacuum leaks. Is there anything else I should check for?

On what is appearantly a totally unreleated note, my power windows worked fine when I took the truck in for service, but now they don't.

Thanks in advance for the troubleshooting advice!

 

[rover4x4]

plugs and wires? I imagine you have the ignition module relocated on the 94's.

 

[deadbeat son]

Plugs and wires are about 3k miles old. Ignition module is in factory location on distributor and has under 1k miles (probably under 500 miles.)

 

[rover4x4]

The mechanic may have overlooked some vacum hoses, or taking them off may caused them to crack?

 

[deadbeat son]

I learned nothing from today's investigation.

First, I checked for vacuum leaks using the old "spray and listen" method and didn't find any issues. Then, I pulled the MAF out, removed the horns, and gave it a good cleaning even though it looked pretty good to begin with.

I still have the somewhat rough idle and a slight stumble just off of idle.

I'll probably give the shop that did the work a call on Monday to see what they have to say.

 

[Mud&Rox]

I had a bad idle on time that drove me nutz tryin to figure it out...it ran fine just idles rough. turned out to be a cracked fan blade lol. prob. isnt your problem but its easy to check

 

[az_max]

I learned nothing from today's investigation.

First, I checked for vacuum leaks using the old "spray and listen" method and didn't find any issues. Then, I pulled the MAF out, removed the horns, and gave it a good cleaning even though it looked pretty good to begin with.

I still have the somewhat rough idle and a slight stumble just off of idle.

I'll probably give the shop that did the work a call on Monday to see what they have to say.

Check other ends of the vacuum lines. Maybe one got knocked loose when they were taking things apart. Or plug off the vacuum connections and see if it idles better.

 

[rover4x4]

I learned nothing from today's investigation.

First, I checked for vacuum leaks using the old "spray and listen" method and didn't find any issues. Then, I pulled the MAF out, removed the horns, and gave it a good cleaning even though it looked pretty good to begin with.

I still have the somewhat rough idle and a slight stumble just off of idle.

I'll probably give the shop that did the work a call on Monday to see what they have to say.

Didnt they fuck it up? I'd be looking for another shop.

 

[deadbeat son]

I had a bad idle on time that drove me nutz tryin to figure it out...it ran fine just idles rough. turned out to be a cracked fan blade lol. prob. isnt your problem but its easy to check

Thanks for the tip. I haven't seen any evidence of this, but I'll have to look closer.

Check other ends of the vacuum lines. Maybe one got knocked loose when they were taking things apart. Or plug off the vacuum connections and see if it idles better.

Thanks, that's a good idea. Unfortunately I won't have time to do that until after I have a chance to run it by the shop and let them give it a quick once over.

Didnt they fuck it up? I'd be looking for another shop.

Not necessarily. It could be coincidental; if they did cause the issue, they should have the opportunity to fix it for me.

 

[rover4x4]

Did you get any resolution?

 

[deadbeat son]

Not yet. I took it in and they spent 30-60 minutes checking the basics. Vacuum lines, plugs & wires, etc. Everything looks right. The more I drive it, the more I'm positive it's a misfire, not just a rough idle. I went ahead and put in new Champion plugs just in case, but that doesn't seem to be it. I'm going to check again for any arcing wires one of these evenings after dark.

After that, I'll take it back to the shop and leave it with them so they can check fuel pressure, put it on the scope, or whatever they need to do to diagnose the issue.

 

[deadbeat son]

Fast forward 13 1/2 months...still having the rough idle issue. I haven't probably put over 500 miles on the Rover in that amount of time

As another thought, the truck came back from the shop with the rough idle and non-working power windows. I solved the window issue; the shop also did some work on the E-brake cable. This required them to get into the console. They had left a center console mounting bolt loose; that bolt held down the ground for the window ECU. I tightened down the bolt and the windows worked.

This got me thinking, could the ground for the ECU be loose causing the issues with the rough idle? I'd love to check that and eliminate it from my mind, but can't find the ground location in the Rover Shop Manual I have (hard copy).

Where is the ECU grounded?

 

[mbrummal]

have you opened up the ECU? they can get corroded and cause problems like that.

 

[Skaramunga]

i too have the idle de diablo.

i have gone thru everything, next is new TPS, & timing adj.

i have one code, p1178 which is annoying & a pain in the ass.

 

[deadbeat son]

have you opened up the ECU? they can get corroded and cause problems like that.

I have not opened the ECU. I'll take a look at that tomorrow. Thanks!

i too have the idle de diablo.

i have gone thru everything, next is new TPS, & timing adj.

i have one code, p1178 which is annoying & a pain in the ass.

I have no codes (pre-OBDII). Good luck!

 

[deadbeat son]

Just an update for future searches. I sold the Rover, and the new owner said the issue was just a plugged injector. It must have happened with the fuel pump and filter change.