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Stalling After Heater Core Replacement/Open System Upgrade


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Hello! Long time lurker (so yes, I do know how to use the search function ;) ), but infrequent poster.

 

The heater core gave up the ghost in my '88 (4.0, 2wd, Asin auto), so I thought while I was replacing it (no fun!), I would take the opportunity to upgrade the cooling system to an open one. I used this guy's guidelines: http://www.olypen.com/craigh/rad.htm

 

The only thing I touched aside from the cooling system was the EVAP canister, the hoses to which were rotted to the point of uselessness. So, I replaced them.

 

A couple of days after I got it all buttoned up -- and thought she was running right nicely -- it started stalling on me. Power loss like she was starving. I got her home and then she wouldn't start, although I can now get her to run for about 10 minutes or so before she starts to idle rough then quit.

 

My first thought was the EVAP canister, so I pulled it. It's not gunked up and air flows through it freely -- man, that thing tastes like crap! Obviously the hoses are new and no kinks. I checked the vapor line from the tank and it appears to be in fine shape and gunk free as well. The line to the air intake is fine too.

 

So, basically I'm asking:

 

A) Did I goof something up? I took my time and tried to be as careful as possible. But if I left some air in the cooling system, could this cause the stalling?

 

B) Could the re-introduction of the EVAP canister back into the system have caused some kind of vacuum imbalance to an engine that got used to not having one? She does have a soul, you know...

 

C) Is this more likely an unrelated and poorly timed issue?

 

D) It's the purge valve solenoid, isn't it? Please tell me it's the purge valve solenoid... ;)

 

 

A few other things: Fuel pump is only a few years old. Plugs, wires, distributor have less than 10k on them. Auxiliary fan is hard wired to run full time. I know, none of this means anything, but I thought it worth a mention...

 

Thanks in advance for any and all help. She's my Daily Driver, and if she doesn't work neither do I! She's also a movie star and I've rented her out to 5 different movies, so she's a breadwinner around here as well. I've owned her for 12 years (I got her from my Father-In-Law -- after much pestering -- who bought her new) and she's been the most reliable thing I've ever owned. This forum has gone a long way to keeping her that way, so thanks for that as well!

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Thanks for the replies!

 

Is it over heating or getting warmer then normal when issues arise?

 

It's from the moment it starts. Cold or hot, makes no difference.

 

I don't think an 88 has a purge valve solenoid. The cannister is just a filter and passively reintroduces the fumes from the fuel tank into the intake to re-burn.

 

It doesn't. I was very sleepy when I wrote that...

 

I'd go back over all my vac lines and see what I left disconnected.

 

I've triple checked them!

 

So here's the new twist: I replaced the MAP sensor -- no difference. I removed and cleaned the IAC and it's socket -- No difference. Replaced the fuel filter -- No difference. I checked the TPS and it was a little out of range; reading 4.1 volts at WOT instead of the required 4.6 - 4.7. Dialed it in spot on, now it's idling at around 4000 rpm!

 

I'd almost consider this a victory, but it's still un drivable!

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The only thing I touched aside from the cooling system was the EVAP canister, the hoses to which were rotted to the point of uselessness. So, I replaced them.

 

B) Could the re-introduction of the EVAP canister back into the system have caused some kind of vacuum imbalance to an engine that got used to not having one? She does have a soul, you know...

Did you possibly re-UN-introduce vacuum somewhere.

 

Sorry to harp on checking vac lines, but it sounds to me like the SOURCE line is off, between the manifold and the cannister causing the high idle. It sounds like the engine is sucking straight air somewhere. Like you say, it's the only thing you touched.

 

The cooling system change would not cause a glitch like this (or maybe the line is off the heater valve, or the vac reservoir and not capped off) IMHO.

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Here's the proper way to adjust a tPS:

 

 

RENIX TPS ADJUSTMENT

 

Before attempting to adjust your TPS be sure the throttle body has been recently cleaned. It's especially important that the edges of the throttle butterfly are free of any carbon build-up.

 

IMPORTANT NOTE: With the Key OFF, and using the positive (red) lead of your ohmmeter, probe the B terminal of the flat 3 wire connector of the TPS. The letters are embossed on the connector itself. Touch the black lead of your meter to the negative battery post. Wiggle the wiring harness where it parallels the valve cover and also over near the MAP sensor on the firewall. If you see more than 1 ohm of resistance, or fluctuation in your ohms reading, some modifications to the sensor ground harness will be necessary. The harness repair must be performed before proceeding. I can provide an instruction sheet for that if needed.

 

MANUAL TRANSMISSION:

RENIX manual transmission equipped XJs have a three-wire TPS mounted on the throttle body. This manual transmission vehicle TPS provides data input to the ECU. The manual transmission TPS has three wires in the connector and they're clearly embossed with the letters A, B, and C. Wire "A" is positive. Wire "B" is ground. Key ON, measure voltage from "A" positive to "B" ground by back-probing the connectors. Note the voltage reading--this is your REFERENCE voltage. Key ON, back-probe the connector at wires "B" and "C". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts. Adjust the TPS until you

have achieved this percentage. If you can't achieve the correct output voltage replace the TPS and start over.

 

AUTOMATIC TRANSMISSION: RENIX automatic transmission equipped XJs have a TPS with two connectors. There is a flat three-wire connector, same as the manual transmission vehicles have, and it is tested the same as the manual transmission equipped vehicles—FOR ENGINE MANAGEMENT RELATED ISSUES.

 

However, the automatic TPS also has a square four-wire connector clearly embossed with the letters A,B,C, and D. It only uses three wires and provides information to the Transmission Control Module. THIS SQUARE FOUR WIRE CONNECTOR IS USED FOR TRANSMISSION/SHIFTING RELATED ISSUES ONLY. Key ON, measure voltage between "A" positive and "D" ground. Note the voltage. This is your REFERENCE voltage. Back-probe the connector at wires "B" and "D". Measure the voltage. This is your OUTPUT voltage. Your OUTPUT voltage needs to be eighty-three percent of your REFERENCE voltage. For example 4.8 volts X .83=3.98 volts. Adjust the TPS until you have achieved this percentage. If you can't, replace the TPS and start over. So, if you have an automatic equipped XJ your TPS has two sides--one side feeds the ECU, and the other side feeds the TCU.

FOR AUTOMATIC TRANSMISSION RELATED ISSUES: Check the four-wire connector side of the TPS.

If you have ENGINE issues check the three-wire connector side of the TPS. For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced.

Revised 08-27-2012

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Sorry I've not replied. It's been raining here (Atlanta), so I haven't popped the hood in a few.

 

ParadiseMJ: I will check all the vacuum a fourth time. The line is definitely on the heater valve, but the valve does tick every now and again when I cut the engine.

 

cruiser54: Thanks for that. I've seen you post that before, so I've slapped myself on the wrist for not following that procedure. I'll do that this afternoon.

 

How old is your O2 sensor?

To be honest, mvusse I don't know when it was last replaced. Pretty sure it's been done in the 12 years I've owned it.

 

Thanks for these tips. I'll run through them all today and report back. I'm missing out on some pretty cool gigs by not having my dependable old DD!

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Whoa! Cruiser54, I just checked the Ohms from terminal 'B' to the negative battery post and it read 13.5! It fluctuated when I wiggled the firewall harness, but remained solid on the valve cover harness.

 

I hear those connectors on the driver's side of the firewall are pretty problematic, so I guess I'll start there with the cleaning then work my way down to the ground point...

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