Top 5% FE Tank with Odd Malfunction

[RH77]

As usual, I have been driving the Integra to keep miles off of the other cars when the kiddos don't need a ride.

Vitals: About 165K miles, only routine maintenance and long-term EcoMods in place. Front LED turn signals + relay installed 1-month prior to problem.

Summary: Stalled, possible EGR / Fuel Trim problem, 39 mpg tank result without extra driving style effort previously used to achieve this FE range.

Condition: On the last tank, I was commuting in town with the manual TC locked, transmission shifted to 4th, and running about 2000 RPM. After cresting a hill and giving it light-to-moderate load, things started going wrong.

Event: The engine lost power and the tach swept from 0-2000 about 5 times -- more throttle was applied and TC disengaged to attempt recover from the problem. Unfortunately it stalled, so I popped it in neutral and tried to start it. It cranked and cranked with no luck, so I coasted into a parking lot.

Diagnostics: No new mods were made (except for LED turn signals up front to test a possible DRL setup) so that was written-off. Under the hood -- nothing that looked completely abnormal. The SG did show a new code: P0400.

I looked it up quickly on my phone and noted "EGR System Malfunction" for other models. After the time to look things up, the engine started immediately, and 400 miles have passed with no problems -- in fact, I recorded one of my best tanks at 39.x MPG and noted more power from reduced throttle input. No more stalling or any other problems.

Research: The isolated problem had me stumped, so I scoured the shop manual for something. First, P0400 is not listed as a trouble code. Second, there's no mention of an EGR system, except in the summary of "acceptable terms" with SAE document J1930 for 2001 and later models with Honda's old descriptor and the SAE Recommended descriptor. It's probably copied to all Honda/Acura manuals. I physically can't locate an exhaust gas recirc system in the manual, or on the vehicle.

The next assumption would be the Cat or O2 sensors -- which might lead to a lean condition and less fuel consumed. Premium fuel is used, with no knocking noted, even under high load and the occasional lugging from manual TC operation. So...

Stumped: I'm reaching out here -- other sources haven't offered anything. If it's an inadvertent EcoMod, I would love to know what it is! Otherwise, I'll (hopefully) continue to enjoy higher FE without trying REALLY hard to get these types of numbers.

-RH77

[bikin' Ed]

Timing belt?

[ksa8907]

could have a vacuum leak, if you feel like throwing time at it, pull the throttle body and clean it really well, don't forget the idle air controller.

[ron]

is fuel pump in the tank? ever run the tank as low as possible to check max mileage? then with 165000 mi on the car and a problem (stalling) that kicks out a code you cant figure out , I suggest a new pump before it leaves you stranded . by the way dont spend a bunch of money on all the easy to change 20-50$ stuff, cut to the chase and change the pump(yourself if possible)

[some_other_dave]

The tach jumping around says to me that you have an ignition problem. I would suspect the ignitor module in the distributor; those are a known weakness in Civic and Integra models.

-soD

[ron]

My son and I spent weeks looking for a problem on his 96 accord 4cyl I changed all the easy stuff as I recall 300ish in goodies, we tested them and went by the codes .when it was all said and done it was an intermittent pump failure. 90bucks I think. just cut into the floor of the trunk to expose the top of the tank, a 6in circle is all thats needed and a cover plate when your done. fairly easy took us about 3hrs.

[RH77]

Yes, I tend to ramble, so I highlighted key points. Feel free to read more if you have time/interest.

Bear in mind FE has significantly increased so I'm really interested if the problem is causing it and/or is detrimental.

Originally Posted by ron

is fuel pump in the tank? ever run the tank as low as possible to check max mileage? then with 165000 mi on the car and a problem (stalling) that kicks out a code you cant figure out , I suggest a new pump before it leaves you stranded . by the way dont spend a bunch of money on all the easy to change 20-50$ stuff, cut to the chase and change the pump(yourself if possible)

Another problem to mention is the fuel gauge. After 1/2-tank it sticks around the 5/8 mark, then drops rapidly. The vast majority of fills have been "below E", but now with the (assumed) unreliable sending unit, the "safe/panic" area was 300-325 miles based on the consumption history.

First, would it pay to borrow a fuel pump gauge to test the non-running pressure output, or with the intermittent problem, should I assume the pump is starting to fail completely? The FP is within the tank -- the manual mentions easy access from the spare tire area, some fiddly parts, but it looks to be within my DIY level. Plus, I don't need to get stranded on my 52-mile / each way commute. I take it that your recommendation would be to replace the pump regardless, or wait for another anomaly?

It doesn't have the "failing pump whine", but I'm sure it's not a universal sign. I'm curious (concerned) to know what crap is in the tank. If the pump is replaced, I would replace the filter again, for the downstream flow component. It's easy and cheap enough, being on the firewall. Maybe after the new pump runs for a tank or 2, in case there is debris churned-up. I'm assuming it's worth it?

Originally Posted by some_other_dave

The tach jumping around says to me that you have an ignition problem. I would suspect the ignitor module in the distributor; those are a known weakness in Civic and Integra models.-soD

The first under-hood items I checked were the wires and boot seat (too many times has a set of cheap wires arced and failed). The cap was replaced at 110K-ish and rotated to full advance for FE (premium fuel used since, plus the warm air intake needs higher octane). Referring to the manual, is this the Ignition Control Module? If it doesn't stall again, should I move on to other fixes?

Originally Posted by ksa8907

could have a vacuum leak, if you feel like throwing time at it, pull the throttle body and clean it really well, don't forget the idle air controller.

Idle is a bit low when warm. The problem with TB and IAC cleaning, is calculating time vs. return on effort. I assume a quick fix would be to spray carb cleaner in the air ports TB and the IAC? (the manual states "not to damage" it, which concerns me a bit on how fragile it is -- shouldn't that statement apply to any part on the car? Kinda funny).

Since it's an automatic, it also has a "Fast Idle Thermo Valve" to check. But I'm just thinking that it would take a significant leak or clog to replicate the stall the way it did. I did learn something new -- engine coolant warms the throttle body through a passage.

Regarding the air's journey into the manifold and cylinder, an auto parts store had a special on SeaFoam this weekend, so I stocked up, and plan to smoke-up the neighborhood on the vac line draw method (considered my usual maintenance process on the family's cars -- except the Insight). It's added to the tank on occasion. Plus the crankcase, short idle time, then oil change. Lost of folks swear by AutoRX or plain water for vacuum line draw to clean the top end, but SF is easy to find and has worked for me.

Originally Posted by bikin' Ed

Timing belt?

Oh geez, I hope not. It's in the "due" range since it (and the water pump) was replaced at 80K. That's about the limit of my DIY for replacement. Without the proper tool, that crank pulley is a bear to remove. The rest is careful placement.

Thanks everyone for the suggestions! It is all covered: air, spark, and fuel. With a new baby, "car-time" is pretty limited. I can sneak some weekend time when the fam comes over to visit/help, so we'll see what develops. The next couple of weeks, it will stay parked while I use a rental car for work -- right now: the Dodge Avenger Base, 2.4L, 4AT. The seats are great, but give the darn thing another gear for FE (and some interior personality! It's OK I suppose. I reviewed it here a while back. They're Daimler leftovers -- the Dart looks like an interesting replacement, but Eminem can keep the 200 (Sebring in new clothes). Did I mention I ramble?

Best FE,
-RH77

[nemo]

The gas gauge and tach have me thinking electrical. Check all connections going to fuel pump and sending unit (in tank unit?) and ignition system, especially grounds.

[ron]

OK ,so here is what my son and I went thru with his problem . we replaced the filter (pain in the butt location )fire wall ,plug wires and plugs. again (I dont like the small electrode tip ) Made a pressure test adaptor for the fuel line , throttle position sensor , got a used distributor from the local wrecking yard , tested every thing again and again. always stalled and would start up again but with increasing frequency in lenght to refire . when I had exhausted every other option and spent hours and lots of cash on things the computer codes pointed to, I finally came to the pump. auto zone unit around a 100bucks ,reused our pickup and sending unit. and it runs great . thats why I say just do it and eliminate it as a problem and dont run below 1/4 tank the fuel cools the pump.

[RH77]

Originally Posted by nemo

The gas gauge and tach have me thinking electrical. Check all connections going to fuel pump and sending unit (in tank unit?) and ignition system, especially grounds.

The grounds definitely need some attention in the engine bay. I've messed with a lot of wiring for mods, so that seems like a reasonable fix. It's easy enough to clean mounting points or add more ground wires (yes, I did that on an Evo as a tuner-mod a while back). If it's clearly corroded at the tank / sending unit, that may be a give-away.

Originally Posted by ron

OK ,so here is what my son and I went thru with his problem . we replaced the filter (pain in the butt location )fire wall ,plug wires and plugs. again (I dont like the small electrode tip ) Made a pressure test adaptor for the fuel line , throttle position sensor , got a used distributor from the local wrecking yard , tested every thing again and again. always stalled and would start up again but with increasing frequency in lenght to refire . when I had exhausted every other option and spent hours and lots of cash on things the computer codes pointed to, I finally came to the pump. auto zone unit around a 100bucks ,reused our pickup and sending unit. and it runs great . thats why I say just do it and eliminate it as a problem and dont run below 1/4 tank the fuel cools the pump.

We were in the thick of the heat/drought here in KC until Isaac dumped enough rain to fill things back up (most of the corn crops not surviving) so it may have been the last straw in it's long, hard life of empty fills and extreme temps. I think the rear seat might have to come out and then a metal cover with a few screws expose the fuel components and it's good to go for replacement.

Looking at the big picture, there may be a fuel delivery and electrical problem (possibly vacuum to fine-tune). It may not have been enough to throw a lean-condition code or emissions fault when the ignition was in flux. We'll see.

Thanks again to everyone for the advice! Like with lots of us here, I learn as I go with vehicle repair and it's appreciated. The next run is 52 miles later this week. It may not happen then, but at least I'm armed with the info to attack it when it does.

Take it Easy...
-RH77