Jump to content
SuperSwede

Vacuum issues / running rich?

Recommended Posts

Lately my comanche has smelled a little bad in the rear and today when I took a look at the spark plugs all six are carbon black, absolute black all over, dry and black.

 

Can´t really say I notised any problem when driving it ...

 

Did a vacuum check and at idle (500rpm)  it was 15 in-hg and at 2200 rpm it was 20 in-hg. What about that is it to low /bad?

Let the throttle snap shut. The vacuum reading shoot up about 5 inches of vacuum higher for a second and then come  down to 15 in-hg again.

 

(Did a check/cleaning  on the EGR valve and it was ok,  also cleaned the IAC and controlled/adjusted the TPS all pretty ok but did it anyway )

Share this post


Link to post
Share on other sites

Seems like a vacuum leak somewhere. Bad/fouled plugs can cause lost of vacuum. What kind of plugs are you running with?

Share this post


Link to post
Share on other sites

Don't know my plugs as good as I should. Maybe someone else can chime in.

Share this post


Link to post
Share on other sites

I'm gonna bet the hose from the throttle body to MAP sensor is compromised.

 

THROTTLE BODY TO MAP SENSOR HOSE FIX

The Renix throttle bodies have a strange and failure prone connector on the side where the MAP supply originates and then runs up to the MAP sensor located on the firewall. This hose/pipe assembly is no longer available for purchase.

The real kicker here is how critical this line is in supplying the correct vacuum signal to the MAP, the most relied upon sensor for the ECU to read regarding air/fuel ratio. Any cracks, melted spots, or loose rubber connectors can cause major starting and driveability issues.

There’s a simple fix though. All that’s required is a 1/8” NPT tap, a new throttle body gasket ( Napa FPG 60742 ), a vacuum fitting (Napa 05703-B102), two vacuum elbows (Napa CRB2670), and a length of new plastic piping (Napa CRB2672).

1-20160126_155433

Remove the throttle body and take it to the workbench.

Using an oiled tap along with a driver, carefully thread the lower of the 2 holes of the throttle body where the old fitting was plugged in. Don’t go too deep. These are pipe threads.

Flush the hole with carb cleaner and inspect for any left over cuttings.
This is an excellent time to do a complete throttle body and IAC cleaning.  See Tip 11.
Take the vacuum fitting (05703-B102 ) and apply a LITTLE bit of thread sealer on the threads only. I prefer Permatex #2 but almost anything is fine.

.1-TB to MAP hose-001

Carefully screw the fitting in until snug.

Install one of the vacuum elbows on the MAP sensor so it points toward the throttle body, and the other vacuum elbow on your new throttle body fitting so it points up to the MAP sensor.
Cut a length of the new plastic tubing (approximately 13 inches) to fit between the vacuum elbows and install it making sure there is enough slack for some engine movement. Route it according to the photo. We don’t want any rubbing or chafing with engine movement.  Not a bad idea to use some contact cement or Gasga-Cinch sparingly on the tubing to elbow connectors.

1-TB to MAP hose

 

 

TB to MAP tube.jpg

Share this post


Link to post
Share on other sites

Sorry to say, but u lose on that one :wink:

 

The MAP to intake line is in mint condition, including the fittings on both side.

Share this post


Link to post
Share on other sites

Vacuum leaks would also cause idle speed to climb, yet you say 500rpms@idle. Possible faulty vacuum gauge????. Quick check the vacuum hose to the Fuel Pressure Regulator(FPR).Looking for leaks or fuel in the line. Does the FPR hold pressure when vacuum is applied or are you sucking fuel? Next test I would think should be a Compression Test (CT) for each cylinder.

Share this post


Link to post
Share on other sites

Did another test today with 800 rpm  and 2000 rpm - vacuum reading 17 and  20 inches.

Fuel pressure at 800 rpm  with vacuum 33 psi and without vacuum 40 psi.

 

Will test the O2 sensor tomorrow,,  got a brand new NGK if needed..

 

 

 

Found this somewhere on a NGK tech side

"Carbon deposits

Carbon deposits appear if the spark plug is frequently operated below its self-cleaning temperature (450 °C) - for example, when only short distances are driven or an incorrect heat rating (too cold) was selected."

 

 

I never drive less than 30 minutes from home so short distances are not the cause.

But maybe the heat grade on the plugs?

 

Gonna put in some Champion RC9YC anyway.

 

 

 

 

 

 

 

Share this post


Link to post
Share on other sites

I would make sure the gap on the spark plugs is set properly   I found that any plugs I have bought recently all need to be gapped properly. .035 if I remember correctly.  I am old-school and ALWAYS confirm the gap on any spark plugs I do, but I know many folks that just put plugs in without checking and setting the gap.

Share this post


Link to post
Share on other sites

Vacuum leaks can be found by spraying carb cleaner at suspected areas BE CAREFUL, propane can be used also and is a bit safer. Look at fuel pressure reg. vac. side VERY close, run with vac hose off to see if fuel is present, may take a while before drip occurs

Share this post


Link to post
Share on other sites

Intake manifold bolts can be loose enough to allow a vacuum leak.

Always a good idea to put a tool on them at least once in a 4.0's lifetime. 

We did that as part of the 30.000 mile tune-up it was so common. 

 

Carb cleaner is a great tool in finding vacuum leaks as stated previously. 

 

If vacuum is verified all good, the MAP sensor could be faulty. 

Share this post


Link to post
Share on other sites

 

I think I have checked all senors there is without any suspicius values.

The same with bolts and carb cleaner can't find any leaks.

 

Don't really have the time  to be in the garage just now due to work and house projects.

Bought a renix monitor today,  maybe it will save me some time..until then I have to drive as it is.

Share this post


Link to post
Share on other sites
5 minutes ago, JustEmptyEveryPocket said:

Can you get the REM by NickinTime? (<<linked to his site) I have heard great things about it from people that own one. Personally I am waiting for the clock replacement version.

 

 

I have Nick's REM and the factory DRB tool.

 

Kinda prefer Nick's.......

Share this post


Link to post
Share on other sites
3 hours ago, JustEmptyEveryPocket said:

Can you get the REM by NickinTime? (<<linked to his site) I have heard great things about it from people that own one. Personally I am waiting for the clock replacement version.

 

Yep that's the one, already on the way, got a fast reply on my order :))

Share this post


Link to post
Share on other sites
9 hours ago, JustEmptyEveryPocket said:

Personally I am waiting for the clock replacement version.

Sorry:hijack:

Like this?:brows: 

image.jpeg

Share this post


Link to post
Share on other sites

Finally some facts, the monitor arrived today and this is the first reading  I got.

Doesent matter how I throttle the 02 voltage is not moving anyway.

 

jeep data 1.jpg

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...