MayDay!! - Hard Accel Killed Idle

[89 MJ]

52 minutes ago, AnotherOldJeepGuy said:

What is the downside to removing the EGR?  Doesn't this mess with the ECU?

People that have to experience emissions testing will not pass without EGR. If you do not have to go through any sort of emissions testing/inspection, there is no downside to deleting it that I have heard. All it does is feed your engine's waste right back through it, reducing efficiency. 

[AnotherOldJeepGuy]

OK got it.

 

Does anyone know of an EGR Delete Kit?  

[Eagle_SX4]

31 minutes ago, AnotherOldJeepGuy said:

Does anyone know of an EGR Delete Kit?  

@boxyjeep sells ones.

https://boxyjeep.com/products/jeep-cherokee-4-0l-egr-plate-1987-1990

 

[AnotherOldJeepGuy]

Great!  If I decided to go this route I'll definitely give boxyjeep the order.

[Gojira94]

1 hour ago, 89 MJ said:

All it does is feed your engine's waste right back through it, reducing efficiency

 

Totally agree with getting rid of the EGR if your state won't ding you for it. Surprisingly, the siphoned exhaust gasses help reduce combustion temps. Two benefits - reduce chances of pre-ignition/ detonation from elevated combustion temps and reduce oxides of Nitrogen (NOx). High NOx is what fails emissions when EGR is deleted or not working properly. Most people don't like the idea of the buildup of combustion by-product in parts of the 'clean' intake side of the engine.

[AnotherOldJeepGuy]

Here in TX emission testing is no longer required for vehicles over 25.  (IIRC I think there are a few TX cities that do require it but not where I live). [Oddly enough the state still collects the same annual fee, just discontinued the test, way to go politicians]

 

I'm not sure I fully understand that last part, "Most people don't like the idea of the buildup of combustion by-product in parts of the 'clean' intake side of the engine", is that a Pro or Con to EGR Delete, sounds like it's a Con?

[Gojira94]

2 hours ago, AnotherOldJeepGuy said:

that last part, "Most people don't like the idea of the buildup of combustion by-product

 

A bit of exhaust is siphoned into the intake manifold upstream of the injectors. There tends to be a gummy/ sooty buildup of stuff that would normally be going out the tailpipe in the EGR valve and in the intake where it's attached. We normally would picture nothing but clean filtered air and fuel going in the intake...

 

Reduction of combustion temps via EGR matters the most for newer generation engines with relatively high compression that depend on EGR for:

1. using all the timing it's calibrated for to produce/ maintain rated power/ torque levels (reduced temps/knock retard)
2. to minimize NOx to meet emissions standards

For an old engine design essentially from the end of the 50s, with 8.8:1 static compression, that runs on low octane fuels, EGR isn't doing a lot for it.

[AnotherOldJeepGuy]

Thanks for all the input so far.  

 

Before I tear in to lots of disassembly, I feel like I need some education.  The INTAKE manifold has multiple vacuum hose connections.  It makes complete sense that the intake side, which is sucking in air, is a great source for creating a vacuum.

 

I also understand that the INTAKE and EXHAUST manifolds share a common set of mounting bolts, and they share a common gasket, so if the bolts work loose it effects both, and therefore effects the vacuum source.  I also note that in this gasket although a common gasket, each orifice is independent, i.e. the intake and exhaust pathways do not share the same air space.

 

Opposite to the Intake Manifold, I see a total of 0 vacuum ports on the Exhaust Manifold.  So since the exhaust path is independent of the intake path (let's for the moment assume the bolts are all tight and the gasket is intact) exactly how would a crack in the exhaust manifold have any effect on the vacuum??

 

 

[Eagle_SX4]

55 minutes ago, AnotherOldJeepGuy said:

exactly how would a crack in the exhaust manifold have any effect on the vacuum??

It does not affect vacuum at all. The problem is that the oxygen sensor reads lean because of the extra air being sucked in to the exhaust and causes the computer to add more fuel. Making the engine run richer than needed, it has a hard time burning the extra fuel, causing the stumbling and poor running. 

[AnotherOldJeepGuy]

Ah OK.  I understand better now, thanks for clearing that up!

 

So it sounds like maybe I have two problems.  A lack of vacuum is for sure (HVAC vent control not there at least at lower RPM, and possibly the reason the brake booster is not boosting) plus also engine stumbling.  Maybe that's a clue.  Maybe what I have is a blown or broken gasket since that would effect both the intake (lack of vacuum) and the exhaust (O2 sensor issue).  The other common point is the block, I don't want to go there....