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Hi everyone!
So I have an up until now faithful 1994 Accord EX 4-door Automatic with VTEC engine. All of a sudden about a month ago it started surging intermittently and it’s gotten worse. I thought it was an idle issue at first (CEL code 14 persists to this day) but now it’s doing it all the time even when the throttle is open. The RPM goes up and down, RRR – RARR — RRR — RARR — you get the idea. It’s bad enough that the engine moves back and forth like its nodding it’s head.
I’ve tried everything I found online as a remedy (thanks to Eric for the videos). Here is what I’ve done so far, some of which seemed to fix it but after a day or two it disappointed:
New spark plugs NGK iridium
New spark plug wires NGK
Royal Purple injector cleaner added to premium gas
Cleaned out original Idle Air Control Valve
Adjusted Fast Idle Thermo Valve
New distributor cap and rotor (did this twice, Duralast then YEC)
New air filter
New pcv valve (oem)
New antifreeze/coolant (oem) — bled system too, after every part change involving coolant lines
Replaced Idle Air Control Valve with New part
Replaced Fast Idle Thermo Valve with New part
New synthetic oil and filter
Disassembled throttle body and cleaned it out very very well including both sides and edges of butterfly and IACV passage, replaced TB gasket
New Throttle Position Sensor calibrated to .5-4.5 (original one tested fine too)
Tried removing vac line (plugged it) and wiring connector from EGR, no change in symptoms
Tried removing wiring connector from IACV, no change in symptoms at speeds above idle
Tried adjusting idle speed screw (paid a mechanic for diagnostic and that’s all he came up with unfortunately) which seemed like a fix but wasn’t.
Tried placing hand in front of open throttle body and engine stalled completely and quickly after hand was sucked up to the opening, my understanding is that pretty much eliminates a vacuum leak as the culprit?
Little to no suction on lower port in TB (FITV)
Lots of suction on upper port in TB (IACV)
Any troubleshooting ideas I can try?
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[quote=”DaCoder” post=156672]Probably, if the surges still happen at full throttle.[/quote]
When the car is acting up it surges / bucks when idling while cold in particular but always when the throttle is opened a bit. When the throttle is opened more (say 2K RPM but I’m not sure), the engine goes to what sounds like redline immediately, there is no smooth transition. Now when it revs that high I can’t tell if it’s still bucking or not. I don’t think it is, just loud as heck. When the car is not acting up, as mentioned this is an intermittent problem, the throttle has the normal smooth transition.
Today I accessed the ECU and backprobed pins A9 and A23 as the troubleshooting flowchart indicates.
Apparently on the OBD1 ECU’s the numbers are odd numbers on top and even on bottom. This picture helped me:
[IMG]http://i133.photobucket.com/albums/q71/GhostAccord/Odds-n-sodds/obd1-pins2.jpg[/IMG]Every time I connected the two pins the IACV clicked. The chart says to then substitute a known-good ECU. As I don’t have one handy I opened up the ECU and studied the components and traces. I noticed several capacitors had leaked a bit of electrolyte – not unusual for old electrolytic caps. Upon closer inspection I noticed that capacitor C11 actually had one leg broken or charred all the way through. Here’s a pic:
[IMG]http://i204.photobucket.com/albums/bb130/7h645764n57/burnt-cap_zpsvmpgjd5i.jpg[/IMG]
Could perhaps be an intermittent contact and getting worse which would explain the intermittent and increasingly worse symptoms.Leaking cap (same value), part C17:
[IMG]http://i204.photobucket.com/albums/bb130/7h645764n57/leaking-ecu-cap-c17_zpsehuido3o.jpg[/IMG]These are both 33uf 35v caps. There is another 33uf 35v on the board that is not doing too great either.
So I’ll order some of these caps and desolder the old and solder the new and see if it’s a miracle or not. If not there would of course still be some doubt as to whether the traces or other components were affected which still would point toward the ECU possibly being at fault. We shall see.
[quote=”ben_tech” post=156760]Today I accessed the ECU and backprobed pins A9 and A23 as the troubleshooting flowchart indicates.
Apparently on the OBD1 ECU’s the numbers are odd numbers on top and even on bottom. This picture helped me:
[IMG]http://i133.photobucket.com/albums/q71/GhostAccord/Odds-n-sodds/obd1-pins2.jpg[/IMG]Every time I connected the two pins the IACV clicked. The chart says to then substitute a known-good ECU. As I don’t have one handy I opened up the ECU and studied the components and traces. I noticed several capacitors had leaked a bit of electrolyte – not unusual for old electrolytic caps. Upon closer inspection I noticed that capacitor C11 actually had one leg broken or charred all the way through. Here’s a pic:
[IMG]http://i204.photobucket.com/albums/bb130/7h645764n57/burnt-cap_zpsvmpgjd5i.jpg[/IMG]
Could perhaps be an intermittent contact and getting worse which would explain the intermittent and increasingly worse symptoms.Leaking cap (same value), part C17:
[IMG]http://i204.photobucket.com/albums/bb130/7h645764n57/leaking-ecu-cap-c17_zpsehuido3o.jpg[/IMG]These are both 33uf 35v caps. There is another 33uf 35v on the board that is not doing too great either.
So I’ll order some of these caps and desolder the old and solder the new and see if it’s a miracle or not. If not there would of course still be some doubt as to whether the traces or other components were affected which still would point toward the ECU possibly being at fault. We shall see.[/quote]
Being of an electrical engineering background, things fail in a waterfall fashion, if you are in Texas I can just buy you an ECM from the local junkyard. I doubt replacing one or two caps will resolve this issue, however it is DEFINITELY worth the shot.
+1 for the circuitry stuff thou.
I could procure a circuit diagram for the ECM if you wish, could tell you for sure if that cap is involved with the idle.[quote=”DaCoder” post=156765]I could procure a circuit diagram for the ECM if you wish, could tell you for sure if that cap is involved with the idle.[/quote]
I’d appreciate that! The 220uf was ‘maybe’ suspect and all three 33uf were probably either bad or gettin’ there. The main suspect is that one at C11 as it was broken, followed by C17 leaking the most.
[quote=”ben_tech” post=156768][quote=”DaCoder” post=156765]I could procure a circuit diagram for the ECM if you wish, could tell you for sure if that cap is involved with the idle.[/quote]
I’d appreciate that! The 220uf was ‘maybe’ suspect and all three 33uf were probably either bad or gettin’ there. The main suspect is that one at C11 as it was broken, followed by C17 leaking the most.[/quote]
IMHO you should order every cap you think even might go bad, future proofing you know.
Leaking caps are common on cars tjis vintage. Look up 5th gen civics and you will see capacitors die a lot these days. Additionally I had a blown capacitor on 94 wagon and it was progressively hard to start until the day it would no longer start at all
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I have owned a 95′ and now own a 94′ Accord EX and I like them because I’ve researched them to holy heck and worked out all the kinks.
5-speed Accord EX F22B1’s don’t surge. Surge like give it power .. and nothing .. not going like it should. Like roar of open throttle body/ yet not equal to it’s propulsion. Could be ignition control module, but I have worked on many F22B1 Accord’s all 5-speed and not once had a surging issue. Though the Auto’s surged all day long, just not going anywhere and fuel mileage suffers greatly.
You’ve done everything that would fix the issue on a manual, though your driving an automatic. I 110% suspect automatic transmission is on it’s way out. Used replacement auto’s are not expensive, search craigslist and find a garage that can install it. The transmission alone is $100 for the auto on craigslist, get one from a low mileage engine.
Once you have the new transmission installed, do not use Honda ATF. Use Amsoil 110% full synthetic transmission fluid to prevent this from every occurring again. AMSOIL also guarantees around 100,000 miles per change on their transmission oils.
For the surging issue, many times it is the IAC, in my experience. Also, depending on how you do it, trying to clean the IAC on that car can make the surging much worse. I’ve seen guys try to clean it, only to develop surging issues as a result. Consequently, they ended up having to replace it.
I think I mis understood what the op meant by surging, like surging at idle? Commonly caused by air in the coolant system. Meaning the Idle Air Control Valve operates by the smooth passing of air free coolant to idle high when cold, low when warm. An up-down like idle is detecting the lack of coolant or air in the passing of the coolant which causes the sensor to read an alternating cold/ hot idle scenario.
To fix that, just lift up the front of the car with a high-lift (24″ or greater) jack at the designated loop point near the radiator. There’s a metal loop, hookable like loop. Lift there. Pull radiator cap, fill reservoir to submerge the overflow hose. Run engine with heat on high, while front of car is high enough that the tip of the radiator cap is surely higher than the heater core. This will force air up as it wants to do and burp until no air buddies and buy a new radiator cap while your at it. What you do is add coolant until you see no more bubbles and once it over-flows, place cap on. Otherwise there is a bleeder valve on top of the thermostat housing near the egr/ vtec solenoid. I run a clear vinyl hose from the bleeder nipple to a clear plastic bottle with a hole in the cap just big enough to have an air tight seal, submerged in 1-3″ of 50/50 coolant. Crack bleeder until no more air bubbles, though lifting the front end up with the cap off is easier. That fixed my ’94 & ’95 accord’s up-down idle after I replaced the thermostat.
[quote=”1chris89″ post=156822]I think I mis understood what the op meant by surging, like surging at idle? Commonly caused by air in the coolant system. Meaning the Idle Air Control Valve operates by the smooth passing of air free coolant to idle high when cold, low when warm. An up-down like idle is detecting the lack of coolant or air in the passing of the coolant which causes the sensor to read an alternating cold/ hot idle scenario.
To fix that, just lift up the front of the car with a high-lift (24″ or greater) jack at the designated loop point near the radiator. There’s a metal loop, hookable like loop. Lift there. Pull radiator cap, fill reservoir to submerge the overflow hose. Run engine with heat on high, while front of car is high enough that the tip of the radiator cap is surely higher than the heater core. This will force air up as it wants to do and burp until no air buddies and buy a new radiator cap while your at it. What you do is add coolant until you see no more bubbles and once it over-flows, place cap on. Otherwise there is a bleeder valve on top of the thermostat housing near the egr/ vtec solenoid. I run a clear vinyl hose from the bleeder nipple to a clear plastic bottle with a hole in the cap just big enough to have an air tight seal, submerged in 1-3″ of 50/50 coolant. Crack bleeder until no more air bubbles, though lifting the front end up with the cap off is easier. That fixed my ’94 & ’95 accord’s up-down idle after I replaced the thermostat.[/quote]
Actually, this is the correct procedure for bleeding the cooling system. It’s a common misconception that the bleeder valve is required to bleed the system. It’s really only there to make filling the system easier. Also, make sure the blower is off when you put the heat on. If not, the fans will never come on.
To the OP. You’ve replaced a lot of parts and checked for vacuum leaks. Given that the problem is intermittent, I’d be looking at a control issue. It seems like it’s getting too much air. The IAC is the primary suspect, but you say you replaced it. Also, it is imperative that you do the correct procedure when you set the idle screw. If not, you do more harm than good. Looks like someone may have stepped in to point you in the right direction there.
I’d be looking for an electrical fault at this point. Perhaps there’s some wires or a connector that’s damaged somewhere. To verify that, you may have to take readings directly at the computer to see if something isn’t right.
When you get to this point with a problem, it may be best to take it to a professional that has the tools and equipment to deal with it. I can type all day long, but without seeing the vehicle for myself, there’s not much I can do. As I said, what you describe is often caused by a bad IAC. Computes on Honda’s very rarely have issues. The only way to diagnose them is to eliminate all other possibilities. If you don’t have the ability to do that, you’re just throwing parts at it.
I’ll post this for good measure.
http://www.ericthecarguy.com/faq/solving-automotive-idle-problems
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
http://www.ericthecarguy.com/faq/solving-automotive-electrical-problems
Good luck and keep us posted.
[quote=”mikerhart27″ post=156820]For the surging issue, many times it is the IAC, in my experience. Also, depending on how you do it, trying to clean the IAC on that car can make the surging much worse. I’ve seen guys try to clean it, only to develop surging issues as a result. Consequently, they ended up having to replace it.[/quote]
Did replace with brand new Denso part same as original. Didn’t fix, think the cleaned original was fine. Passes all the tests from IACV troubleshooting flowchart so must be something like the ECU.
[quote=”1chris89″ post=156822]I think I mis understood what the op meant by surging, like surging at idle? Commonly caused by air in the coolant system.[/quote]
Thanks for the suggestion.
When the car is acting up it surges / bucks when idling while cold in particular but always when the throttle is opened a bit. When the throttle is opened more (say 2K RPM but I’m not sure), the engine goes to what sounds like redline immediately, there is no smooth transition. Now when it revs that high I can’t tell if it’s still bucking or not. I don’t think it is, just loud as heck. When the car is not acting up, as mentioned this is an intermittent problem, the throttle has the normal smooth transition. All of this happens in Park so not sure if the transmission could be it. Also no transmission codes only code 14 from ECU.
I have tried bleeding the coolant system. I drained and refilled and jacked up the front the first time I tried this (a month ago before replacing anything). Didn’t cure it. Obviously I’ve replaced some parts since so it may bear re-doing with the jack. I’ve used Eric’s method with the special funnel set each time after replacing anything with coolant lines. Only thing I could try that I didn’t do is squeezing the radiator hoses during the procedure. Some guys do that.
[quote=”EricTheCarGuy” post=156852]Good luck and keep us posted.[/quote]
Thanks Eric. I appreciate all of the good info and videos they have been very helpful.
[quote=”ben_tech” post=156873][quote=”EricTheCarGuy” post=156852]Good luck and keep us posted.[/quote]
Thanks Eric. I appreciate all of the good info and videos they have been very helpful.[/quote]
Honestly I didn’t know you had an A/T, place it in neutral, when the engine is acting up, see if it solves it. The TCM on this car also might cause issues.
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